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THE  LIBRARY 

OF 

THE  UNIVERSITY 

OF  CALIFORNIA 

DAVIS 

GIFT  OF 

ROBERT  I.   TEKMEy 


Indostrial  Cbemical  Inslitule  of 


Digitized  by  the  Internet  Archive 

in  2007  with  funding  from 

Microsoft  Corporation 


http://www.archiye.org/details/examiwaterOOIeffrich 


Examination  of  Water  ^ 


SANITARY  AND  TECHNIC  PURPOSES 


BY  CHEMICAL 

AND  BACTERIOLOGIC 

METHODS. 


BY 

HENRY  LEFFMANN,  A.M.,   M.D.,   Ph.D., 

PROFESSOR     OF     CHEMISTRY     IN    THE    WOMAn's    MEDICAL     COLLEGE     OF     PENNSYL- 
VANIA  AND   IN   THE   WAGNER    FREE    INSTITUTE   OF    SCIENCE;    PRESI- 
DENT (19O1)  OF   THE    engineers'    CLUB   OF    PHILADELPHIA; 
AND    VICE-PRESIDENT    (190I-C2)    BRITISH    SOCIETY 
OF    PUBLIC   ANALYSTS. 


SIXTH  EDITION,  REVISED  AND  ENLARGED,   WITH 
ILL  USTRA  TIONS. 


.<" 


PHILADELPHIA 

BLAKISTON'S  SONS   &  CO. 

IOI2    WALNUT   STREET 
1909 


UttlVliJbC::iITY  of  CAUFftSaia 

PAvia 


Copyright,  1909,  by  P.  Blakiston's  Son  &  Co. 


.     F.     FELL    COMPANY 
PRINTERS 
PHILADELPHIA 


Wl^T^ 


I    DEDICATE   THIS    BOOK    TO   THE 
MEMORY    OF 

/iDi?  /iDotber, 

TO    WHOSE    WISE    PRECEPT   AND    EXAMPLE 

IN    MY    BABYHOOD 

I   OWE   WHATEVER   MERIT   MY   MANHOOD   YEARS 

MAY   SHOW. 


PREFACE 


In  the  present  edition,  numerous  revisions  have 
been  made,  but  the  plan  of  the  book  has  not  been 
disturbed.  Among  the  additions  to  this  edition 
are:  the  precipitation  (nitron)  method  for  ni- 
trates ;  the  bile-lactose  method  for  the  colon  bacil- 
lus ;  a  description  of  the  method  devised  by  Jack- 
son and  Melia  for  detecting  the  typhoid  bacillus ; 
notice  of  a  special  reagent  for  detecting  excess 
of  aluminum  compounds. 

In  the  five  editions  which  have  been  issued, 
the  book  has  seen  notable  changes  in  the  attitude 
of  experts  toward  certain  methods.  When  the 
first  edition  was  issued  (jointly  with  Dr.  William 
Beam) ,  bacteriologists  were  enthusiastically  claim- 
ing to  be  able  to  determine  easily  the  presence 
or  absence  of  disease-producing  microbes  in  water, 
and  asserting  that  sanitary  analysis  of  water  by 
chemical  methods  was  about  to  become  a  mat- 
ter of  history.  At  present,  the  value  of  routine 
chemical  analysis  is  generally  recognized.  Upon 
this  point,  and  also  on  the  question  of  the  inherent 
danger  of  unfiltered  surface  water  even  when  not 


PREFACE. 

receiving  sewage  directly,  the  book  took  decided 
stand,  and  the  development  of  the  views  of  ex- 
perts has  fully  justified  it.  Long  experience  has 
convinced  me  that  for  determining  the  potability 
of  water,  the  determinations  of  chlorin,  nitrates, 
and  nitrites  afford  the  most  satisfactory  indica- 
tions, and  that  the  figures  •for  nitrogen  or  ammo- 
nium (so-called  ''free  ammonia")  and  nitrogen  by 
permanganate  (so-called  ''albuminoid  ammonia") 
are  of  much  less  value  than  is  generally  supposed. 
The  suggestion  of  Woodman,  that  phosphates 
afford  a  useful  datum,  is  worthy  of  special  atten- 
tion. 

1839  N.  17th  Street, 
Philadelphia,  January,  1909. 


CONTENTS. 


PAGES 

Natural  History  and  Classification  of  Natural  Waters. 
Rain     Water — Surface     Water — Subsoil     Water — 

Deep  Water, 1-7 

Analytic  Operations. 

Sanitary  Examinations: 

Collection  and  Preliminary  Examination — Total 
Solids — Chlorin — ^Nitrogen  in  Ammonium  Com- 
pounds and  Organic  Matter — ^Nitrogen  as  Ni- 
trates— Nitrogen  as  Nitrites — Oxygen-consuming 
Power — Phosphates — Dissolved  Oxygen — Pois- 
onous Metals — Biologic  Examinations 8-90 

Technic  Examinations: 

General  Quantitative  Analysis — Spectroscopic  An- 
alysis— Specific  Gravity, 91-113 

Interpretation    of    Results. 

Statement  of  Analysis — Sanitary  Applications — 
Action  of  Water  on  Lead — Technic  Applica- 
tions— Boiler  Waters — Sewage  Effluents — Puri- 
fication of  Water — Identification  of  Source  of 
Water, 1 14-141 

Data  for  Calculation 142, 143 

Index. 


NATURAL   HISTORY  AND  CLASSIFICA- 
TION OF  WATER. 

Pure  water  is  an  artificial  product.  Natural 
waters  always  contain  foreign  matters  in  solution 
and  suspension,  varying  from  mere  traces  to  very 
large  proportions.  The  properties,  effects,  and 
uses  of  water  are  considerably  modified  by  these 
ingredients,  and  the  object  of  analysis  is  to  as- 
certain their  character  and  amount.  Since  these 
are  largely  dependent  on  the  history  of  the  water, 
a  classification  based  on  this  will  be  convenient. 
We  may  distinguish  four  classes  of  natural  waters : 

Rain  Water. — Water  precipitated  from  the 
atmosphere  under  any  conditions,  and  therefore 
including  dew,  frost,  snow,  and  hail. 

Surface  Water. — All  collections  of  water  in  free 
contact  with  the  atmosphere,  as  in  streams,  seas, 
lakes,  or  ponds. 

Subsoil  or  Ground  Water. — Water  not  in  free 
contact  with  the  atmosphere,  percolating  or 
flowing  thru  soil  or  rock  at  moderate  distance  be- 
low the  surface,  and  derived  in  large  part  from 
the  rain  or  surface  water  of  the  district. 

Deep  or  Artesian  Water. — Water   accumulated 


2  HISTORY    AND   CLASSIFICATION. 

at  considerable  depth  below  the  surface,  from 
which  the  subsoil  water  of  the  district  has  been 
excluded  by  difficultly  permeable  strata. 

Rain  water,  when  gathered  in  the  open 
country  and  in  the  later  period  of  a  prolonged 
rain  or  snow,  is  the  purest  form  of  natural  water. 
When  collected  directly,  it  contains  but  little  solid 
matter,  this  consisting  principally  of  ammonium 
compounds  and  particles  of  organic  matter, 
living  and  dead,  gathered  from  the  atmosphere. 
In  districts  near  the  sea  an  appreciable  amount  of 
chlorids  will  be  present.  It  is  obvious  that  a  pro- 
longed rain  will  wash  out  the  air,  but  since  storms 
are  usually  attended  by  wind,  fresh  portions  of  air 
are  continually  flowing  in,  and  thus  the  water 
never  becomes  perfectly  pure.  Rain  water  col- 
lected in  inhabited  districts  is  usually  quite  impure. 

Surface  Water. — Rain  water  in  part  flows  off  on 
the  surface,  and  gains  in  the  proportion  of  sus- 
pended and  dissolved  matters,  the  former  being 
found  in  large  amount  when  the  rainfall  is  profuse. 
The  wearing  action  of  water  is  dependent  on  the 
amount  and  character  of  these  suspended  mater- 
ials. From  the  higher  levels  of  a  watershed,  the 
streams,  more  or  less  in  the  form  of  torrents, 
gather  into  larger  currents,  and,  reaching  lower 
levels,  become  slower  in  movement,  and  deposit 
much  of  the  suspended  matter.  By  admixture 
of  the  waters  from  widely  separated  districts  the 


SUBSOIL    WATER.  3 

character  and  amount  of  the  dissolved  matters 
are  much  modified. 

It  is  obviously  impossible  to  establish  close 
standards  of  composition  for  surface  waters.  In 
the  case  of  rain  water,  falling  on  the  surface  of  un- 
disturbed, unpopulated  territory,  the  amount  of 
solids  dissolved  will  be  small,  and  will  consist  prin- 
cipally of  carbonates  and  sulfates.  The  water  of 
lakes  and  rivers  is,  however,  in  part  derived  from 
springs,  which  may  proceed  from  great  depths,  and 
thus  introduce  substances  not  easily  soluble  in 
surface  water,  nor  derivable  from  the  soil  of  the 
district. 

The  exposure  to  light  and  air  which  surface 
water  undergoes  results  in  the  absorption  of  oxy- 
gen and  loss  of  carbonic  acid,  together  with  the 
oxidation  of  the  organic  matter.  The  diminution 
of  the  rapidity  of  the  current  permits  the  deposi- 
tion of  the  suspended  matters,  and  this  occurs 
especially  as  the  river  approaches  the  sea,  not  only 
from  the  retarding  influence  of  the  tidal  wave,  but 
from  the  precipitating  action  of  the  salt  water. 

Subsoil  Water. — Water  that  penetrates  the  soil 
passes  to  different  depths,  according  to  the  porosity 
and  arrangement  of  the  strata.  As  a  rule,  it 
descends  until  it  reaches  formations  but  slightly 
pervious,  upon  the  level  of  which  it  accumulates. 
In  the  upper  layers  of  soil  it  dissolves  mineral  and 
organic    ingredients,    and   becomes    impregnated 


4  HISTORY    AND    CLASSIFICATION. 

with  minute  organisms,  thru  the  agency  of  which 
the  organic  matter  undergoes  important  trans- 
formations. The  water,  constantly  accumulating, 
gradually  flows  along  the  incline  of  the  impervious 
stratum,  or  thru  its  fissures,  and  may  either  pass 
downward  or  emerge  in  the  form  of  a  spring. 

Much  difference  is  observed  in  the  composition 
of  subsoil  waters,  but  as  a  general  rule  they  con- 
tain small  amounts  of  mineral  substances  and 
organic  matter.  In  populated  districts,  however, 
a  marked  change  is  produced  through  admixture 
with  water  containing  animal  and  vegetable  prod- 
ucts in  various  stages  of  decomposition.  It  is 
probably  the  organic  matters  containing  nitrogen 
that  are  of  importance.  These  are  mostly  un- 
stable, and  decompose,  partly  by  oxidation, 
partly  by  splitting  up  into  simpler  forms — changes 
in  most  cases  brought  about  by  microbes.  The 
nitrogen  is  in  part  converted  into  ammonium 
compounds,  but  a  considerable  portion  suffers 
further  oxidation,  and  in  association  with  the 
mineral  substances  present  forms  nitrites  and 
nitrates,  especially  the  latter.  This  is  called 
*' nitrification.*' 

Nitrification  takes  place  under  the  influence  of 
microbes,  the  habitat  of  which  does  not  extend 
very  far  below  the  surface  of  the  soil.  Several 
forms  with  active  nitrifying  powers  have  been 
isolated  and  described.     The  nitrifying  action  is 


DEEP    WATER.  5 

often  exerted  upon  the  ammonium  compounds 
formed  from  the  organic  matter.  The  presence  of 
some  substance  capable  of  neutraHzing  acids  is 
usually  necessary  to  continuous  action.  Calcium 
and  magnesium  carbonates  fulfil  this  function. 
Nitrates  are  the  final  result  of  this  action ;  nitrites 
are  present  at  any  given  time  only  in  small  quan- 
tity. Denitrification — that  is,  the  reduction  of 
nitrates  and  nitrites  to  ammonium  compounds — 
takes  place  also  under  the  influence  of  microbes, 
and  is  especially  apt  to  occur  when  considerable 
quantities  of  decomposing  organic  matter  are  in- 
troduced. Several  species  of  denitrifying  bacilli 
have  been  described.  A  partial  reduction  some- 
times occurs,  and  a  notable  proportion  of  nitrites 
is  found,  but  in  the  presence  of  actively  decompos- 
ing organic  matter,  such  as  that  in  sewage,  a  com- 
plete reduction,  even  to  the  liberation  of  nitrogen, 
may  occur. 

Deep  Water. — Water  which  penetrates  the 
fissures  of  the  fundamental  rock-formations  may 
pass  to  great  depths,  and  by  following  the  lines  of 
the  lowest  and  least  permeable  strata,  may  be 
transported  to  points  far  removed  from  those  at 
which  it  was  originally  collected.  The  chemical 
changes  thus  induced  include  most  of  those  which 
take  place  at  higher  points,  but  the  increase  of 
pressure  and  temperature  confers  increased  solvent 
power.     Carbonic  acid  will  accumulate  and  pro- 


6  HISTORY    AND    CLASSIFICATION. 

duce  conditions  favorable  to  the  solution  of  cal- 
cium, magnesium,  and  iron  carbonates;  iron  and 
manganese  oxids  may  be  converted  into  car- 
bonates and  then  dissolved.  Sulfates  are  reduced 
to  sulfids,  and  these  subsequently,  by  the  action 
of  carbonic  acid,  yield  hydrogen  sulfid.  Organic 
matter,  living  and  dead,  plays  an  important  part, 
determining  the  reduction  of  ferric  compounds  to 
ferrous,  and  of  the  sulfates  to  sulfids,  and  is  itself 
converted  ultimately  into  ammonium  compounds, 
notable  quantities  of  which  are  often  found  in  deep 
waters.  Further,  it  is  found  that  nitrates  and 
nitrites  are  present  only  in  small  amount,  except 
from  certain  strata  rich  in  organic  matter.  In 
some  cases  the  water  acquires  very  high  tempera- 
ture, and  dissociation  of  rocks  occurs  with  solution 
of  considerable  amounts  of  silicic  acid,  which  is 
ordinarily  but  sparingly  soluble  in  water. 

Masses  of  water  thus  accumulated  under  heat 
and  pressure  may  find  their  way  to  the  surface 
either  thru  natural  fissures  or  be  reached  by 
borings. 

While  X  J  absolute  line  can  be  drawn  between 
deep  and  subsoil  waters,  yet  it  will,  in  most  cases, 
be  found  that  the  deep  water  of  a  given  district, 
whether  obtained  thru  natural  or  artificial  chan- 
nels, will  be  decidedly  different  in  composition 
from  the  subsoil  or  surface  water  of  the  same,  and 
that  the  rocks  overlying  the  veins  of  water  will 


DEEP    WATER.  7 

contain  one  or  more  strata,  difficultly  permeable  to 
water,  and  therefore  preventing  direct  communi- 
cation. The  characteristic  differences  between 
surface,  subsoil,  and  deep  waters  are  given  in  a 
table  under  the  section  on  interpretation  of  re- 
sults. 


ANALYTIC  OPERATIONS. 

SANITARY  EXAMINATIONS. 

COLLECTION  AND  PRELIMINARY  EX- 
AMINATION   OF   SAMPLES. 

Great  care  must  be  taken  in  collecting  water 
samples,  in  order  to  secure  a  fair  representation  of 
the  supply  and  to  avoid  introduction  of  foreign 
matters.  The  five-pint  green  glass-stoppered 
bottles  used  for  holding  acids  are  suitable  for  con- 
taining the  samples.  The  contents  of  one  such 
bottle  will  suffice  for  most  sanitary  or  technic 
examinations.  Boxed  bottles  which  are  furnished 
by  dealers  are  convenient  for  transportation. 
They  are  usually  provided  with  a  hinged  lid  which 
can  be  fastened,  if  deemed  necessary,  by  a  pad- 
lock. The  green  glass-stoppered  bottles  may  be 
fitted  in  such  an  arrangement.  Crated  demijohns 
are  also  made  for  forwarding  water.  The  larger 
sizes  are  well  adapted  for  samples  which  are  to  be 
subjected  to  elaborate  analysis.  Stone  jugs,  casks, 
or  metal  vessels  should  not  be  employed.  All 
bottles  must  be  well  rinsed  several  times  with  the 
water  to  be  examined,  filled,  and  the  stopper  tied 

8 


SANITARY    EXAMINATIONS.  9 

down  or  fastened  by  stretching  a  rubber  finger-cot 
over  the  stopper  and  Hp.  If  corks  are  used,  they 
should  be  new  and  well  rinsed.  Wax,  putty, 
plaster,  or  similar  material  should  not  be  used. 
It  is  not  necessary  to  sterilize  the  bottles  when  only 
chemical  tests  are  to  be  made. 

In  taking  samples  from  lakes,  slow  streams,  or 
reservoirs,  it  is  necessary  to  submerge  the  bottle 
so  as  to  avoid  collecting  any  water  that  has  been 
in  immediate  contact  with  the  air.  In  the  ex- 
amination of  public  water-supplies,  the  sample 
should  be  drawn  from  a  hydrant  in  direct  con- 
nection with  the  main,  and  not  from  a  cistern, 
storage -tank,  or  dead  end  of  a  pipe.  In  the  case 
of  pump- wells,  a  few  gallons  of  water  should  be 
pumped  out  before  taking  the  sample,  in  order  to 
remove  that  which  has  been  standing  in  the  pipe. 

In  all  cases,  care  should  be  taken  to  fill  the 
vessel  with  as  little  agitation  with  air  as  possible. 

It  is  important  that  with  each  sample  a  record 
be  made  of  those  surroundings  and  conditions 
which  might  influence  the  character  of  the  water, 
particularly  in  reference  to  sources  of  pollution, 
such  as  proximity  to  cesspools,  sewers,  or  manu- 
facturing establishments.  The  character  and  con- 
dition of  the  different  strata  of  the  locality  should 
be  noted  if  possible. 

Determinations  of  nitrogen  existing  as  ammon- 
ium compounds  and  as  organic  matter,  and  of 


lO 


ANALYTIC    OPERATIONS. 


oxygen-consuming  power,  should  be  made  upon 
the  sample  in  the  original  condition,  whether  tur- 
bid or  clear,  but  all  other  estimations  should  be 
made  upon  the  clear  liquid.  Tur- 
bid waters  may  be  clarified  by 
standing  or  by  filtration;  for  the 
latter  purpose  Schleicher  &  Schull's 
extra  heavy  598  paper  is  the  best. 
In  many  cases  the  suspended  matter 
can  not  be  entirely  removed  by 
filtration,  and  subsidence  must  be 
resorted  to.  The  use  of  a  small 
quantity  of  alum,  or  aluminum  sul- 
fate, as  now  applied  in  the  purifica- 
tion of  drinking  water,  will  some- 
times be  satisfactory  as  a  means  of 
clarifying  samples.  For  the  quan- 
titative determination,  the  sedi- 
ment from  a  known  volume  of  the 
water  is  collected  on  a  tared  filter, 
dried,  and  weighed. 

The  water  from  newly  dug  wells 
is  generally  turbid,  and  the  deter- 
minations are  best  made  after 
filtration;  but  the  results  will  be 
unsatisfactory,  showing  a  higher 
proportion  of  organic  matter  than 
will  be  found  when  the  supply  becomes  clear. 
For  taking   samples   at   considerable  depths  the 


lI'liiiKNTZSiSONS 


Fig.  I. 


I 


SANITARY    EXAMINATIONS.  II 


bottle  shown  in  Fig.  i  will  answer,  but  samples  so- 
collected  will  not  serve  for  determination  of  dis- 
solved gases. 

Collection  of  Samples  for  Bacteriologic  Exam- 
ination.— Bacteriologic  examinations  are  of  little 
value  unless  made  promptly  on  samples  that  have 
been  collected  with  precautions  against  contam- 
ination. The  inoculation  of  the  culture-medium 
is  best  done  at  the  source.  If  this  is  not  possible, 
glass-stoppered  bottles  holding  about  200  c.c, 
which  have  been  thoroughly  sterilized,  with  stop- 
pers in  place,  in  a  hot-air  oven  at  150°  C,  must  be 
used  for  collection.  They  should  be  rinsed  on  the 
outside  with  the  water,  dipped  below  the  surface, 
the  stopper  withdrawn,  and  again  inserted  when 
the  bottle  is  full.  If  these  are  to  be  transported 
any  distance,  they  should  be  packed  in  ice.  For 
the  collection  of  samples  below  the  surface  of  the 
water,  the  bottle  shown  in  Fig.  i  is  recommended 
by  Abbott.  The  bottle  having  been  previously 
thoroughly  sterilized,  is  sunk  to  the  proper  depth, 
and  the  stopper  is  then  lifted  by  a  special  cord  and 
held  until  the  bottle  is  full,  when,  the  cord  being 
released,  the  stopper  falls.  Before  taking  out 
portions  for  test  the  lip  and  stopper  must  be 
well  sterilized  by  strong  alcohol  and  by  care- 
ful heating,  and,  after  cooling,  washing  with 
sterilized  water. 

Color. — A  colorless  glass  tube,  two  feet  long  and 


12  ANALYTIC    OPERATIONS. 

two  inches  in  diameter,  is  closed  at  each  end  with 
a  disc  of  colorless  glass.  An  opening  for  filling 
and  emptying  the  tube  should  be  made  at  one  end, 
either  by  cutting  a  small  segment  off  the  glass 
disc,  or  cutting  out  a  small  segmental  section  of 
the  tube  itself  before  the  disc  is  cemented  on. 
A  good  cement  for  such  purposes  is  the  following : 

Caoutchouc, 2  parts. 

Mastic, 6 

Chloroform, 100       '' 

The  ingredients  are  mixed  and  allowed  to  stand 
for  a  few  days.  The  cement  should  be  used  as 
soon  as  solution  is  effected,  as  it  becomes  viscid  on 
standing. 

The  tube  must  be  about  half  filled  with  the 
water  to  be  examined,  brought  into  a  horizontal 
position,  level  with  the  eye,  and  directed  toward  a 
brightly  illuminated  white  surface.  The  com- 
parison of  tint  has  to  be  made  between  the  lower 
half  of  the  tube  containing  the  water  under  ex- 
amination and  the  upper  half  containing  air  only. 

A  more  convenient  form  of  tube  is  made  by 
attaching  brass  screw-nipples  to  each  end  of  the 
tube,  and  closing  these  by  screw-caps  carrying 
plate-glass  discs.  Such  tubes  can  be  obtained 
from  dealers  in  chemical  apparatus.  It  is  obvious 
that  various  methods  of  comparing  color  and 
turbidity  may  be  devised,  but  data  so  obtained  are 


I 


SANITARY    EXAMINATIONS.  13 


of  little  analytic  value,  and  even  that  little  is 
limited  to  samples  closely  analogous  in  character. 

Hazen  has  devised  a  standard  for  color  com- 
parison which  he  claims  as  capable  of  most  satis- 
factory use  on  all  ordinary  waters.  It  is  based 
upon  the  modification  of  a  solution  of  platinum 
chlorid  by  a  solution  of  cobalt  chlorid,  as  follows : 

1.246  grams  of  potassium  platinum  chlorid 
(corresponding  to  0.5  gram  of  platinum)  and  i 
gram  of  cobalt  chlorid  (corresponding  to  0.25 
gram  of  cobalt)  are  dissolved  in  water,  100  c.c.  of 
strong  hydrochloric  acid  added,  and  the  solution 
made  up  to  1000  c.c.  It  keeps  well,  even  when 
exposed  to  the  light.  For  comparison,  1,2,3,  ^"^c., 
of  the  stock  solution  are  diluted  to  50  c.c.  in 
Nessler  tubes.  These  correspond  to  o.i,  0.2,  0.3, 
etc.,  degrees  of  the  color  standard.  These  also 
keep  for  a  long  time  if  protected  from  dust. 
Direct  comparison  in  200  mm.  tubes  is  generally 
sufficient.  If  the  shade  of  color  is  not  exactly 
that  of  the  water,  more  cobalt  may  be  added,  the 
platinum  being  constant.  Hazen  expresses  the 
result  in  any  case  in  terms  of  ''the  amount  of 
platinum  in  parts  per  10,000,  which  in  acid  solu- 
tion with  so  much  cobalt  as  will  match  the  hue, 
produces  an  equal  color  in  distilled  water." 

Lovibond's  tintometer  is  probably  the  best 
means  of  making  color  comparisons. 

Odon — Put  about  150  c.c.  of  the  water  into  a 


14  ANALYTIC    OPERATIONS. 

clean,  wide-mouthed  250  c.c.  stoppered  bottle, 
which  has  been  previously  rinsed  with  the  same 
water ;  insert  the  stopper  and  warm  the  water  in  a 
water-bath  to  100°  F.  Remove  the  bottle  from 
the  water-bath  and  shake  it  rapidly  for  a  few 
seconds;  remove  the  stopper,  and  immediately 
note  if  the  water  has  any  smell.  Insert  the  stopper 
and  repeat  the  test. 

In  a  polluted  water  the  odor  will  sometimes 
give  a  clue  to  the  origin  of  the  pollution. 

Turbidity. — Several  methods  for  expressing  de- 
gree of  turbidity  have  been  used.  Whipple  and 
Jackson,  after  comparing  these,  find  that  finely 
powdered  diatomaceous  earth  is  satisfactory. 
The  material  is  ignited,  ground  to  a  powder  that 
will  pass  thru  a  200-mesh  sieve,  dried  at  100°  C, 
cooled  in  a  desiccator,  and  kept  in  a  well-stoppered 
bottle.  A  strong  standard  is  prepared  by  adding 
I  gram  of  this  powder  to  1000  c.c.  of  water,  and  12 
dilute  standards  by  mixing  quantities  of  the  strong 
standard  in  amount  from  i  to  10  c.c,  increasing  by 
0.5  c.c,  to  quantities  of  distilled  water  sufficient 
to  make  100  c.c  in  each  case.  The  dilute  stand- 
ards are  kept  in  tightly  corked  tubes  and  shaken 
several  times  when  used  for  comparison.  If  new 
corks  are  used,  they  should  be  well  boiled  in  water 
to  extract  coloring-matter.  If  the  sample  is  of 
high  turbidity,  it  must  be  diluted  by  a  known 
volume  of  water.     The  record  is  made  by  noting 


SANITARY    EXAMINATIONS.  IS 

the  strength  of  the  standard  tube  that  is  nearest 
in  turbidity  to  the  sample,  the  tubes  being  held 
together  and  viewed  from  the  side.  The  tube  con- 
taining the  sample  must  be  uniform  in  size  and 
quality  with  those  containing  the  standard. 

Reaction. — Many  indicators  have  been  proposed 
for  testing  reaction.  As  water  always  contains 
carbonic  acid  or  acid  carbonates,  tests  may  be 
misleading,  unless  made  both  on  the  cold  water 
and  on  a  sample  immediately  after  thoro  boiling. 
I  have  had  good  results  with  sodium  alizarin- 
monosulfonate.  The  solution  may  be  made  by 
dissolving  one  gram  in  loo  c.c.  of  water.  It  keeps 
well.  For  use  a  few  drops  are  added  to  a  con- 
venient volume  of  the  water,  and  decinormal  acid 
(or  alkali  as  required)  added  until  the  color  change 
is  noted.  The  indicator  is  yellow  when  acid,  red 
when  alkaline,  brownish  when  neutral. 

A  special  method  of  determining  reaction  has 
been  recommended  by  the  laboratory  committee 
of  the  American  Public  Health  Association.  The 
indicator  is  made  by  dissolving  o.i  gram  of  sodium 
erythrosin  in  looo  c.c.  of  water,  loo  c.c.  of  the 
sample  is  put  into  a  250  c.c.  fiask,  and  2.5  c.c.  of  the 
indicator  solution  added  with  5  c.c.  of  chloroform. 
Decinormal  acid  is  added  drop  by  drop,  shaking 
after  each  addition.  The  disappearance  of  the 
color  of  the  reagent  indicates  that  the  alkalinity 
has  been  overcome. 


i6 


ANALYTIC    OPERATIONS. 


Other  indicators  are  used  in  special  cases,  which 
will  be  noted  in  the  proper  connection.  Most 
indicators  are  freely  soluble  in  water,  the  solu- 
tion being  made  by  dissolving  about  i  gram  in 
loo  c.c.  Phenolphthalein  must  be  dissolved  in 
alcohol  in  the  above  proportion. 


TOTAL  SOLIDS. 

A  platinum  basin  holding  loo  c.c.  will  be  found 

convenient  for  this  determination.    This  will  weigh 

about  45  grams.     It  should 

be  kept  clean  and  smooth 

by  frequent  burnishing  with 

sand,  a  little  of  which  should 

be  placed  in  the  palm  of  the 

hand,   moistened,   and   the 

dish  gently  rubbed  against 

it.     Very  fine  sea-sand  with 

round,  smooth  grains  is  the 

only  kind  suitable  for  this 

purpose .    Coarse  river  sand, 

tripoli,    or   other   rough   scouring  powders   must 

not  be  employed.     If  proper  care  is  taken,  the 

luster  of    the   metal  will    be   retained,   and  the 

loss  in  weight  will  be  trifling.     The  inner  surface 

can    generally    be    cleaned    by    treatment    with 

hydrochloric    acid,    rinsing,    and,    if    necessary, 

burnishing  with  sand.     Neglect  of  these  precau- 


FlG.    2. 


SANITARY    EXAMINATIONS.  1 7 

tions  will  soon  lead  to  serious  damage  to  the  dish. 
A  small,  smooth  slab  of  iron  or  marble  is  con- 
venient to  set  it  on  while  cooling.  When  being 
heated  over  the  naked  flame,  the  dish  should  rest 
on  a  triangle  of  iron  wire,  covered  with  pipe- 
stems.  Dishes  of  pure  nickel  are  not  satisfactory 
substitutes  for  those  of  platinum. 

Platinum-pointed  forceps  should  be  used  in 
handling  the  dish.  The  platinum  terminals  may 
be  kept  bright  and  clean  by  the  use  of  sand. 

The  low-temperature  burner,  used  as  shown  in 
figure  2,  will  be  found  a  very  convenient  substitute 
for  the  water-bath  and  hot-air  oven.  The  inlet 
pipe  is  very  short  and  soon  becomes  so  hot  as  to 
injure  the  rubber  tube.  To  avoid  this  it  may  be 
lengthened  by  means  of  a  piece  of  gas-pipe  about 
12  centimeters  long,  or  the  junction  may  be 
wrapped  with  a  rag,  the  ends  of  which  dip  into 
water.  By  capillary  attraction  the  rag  is  kept 
moist  and  cool. 

The  determination  of  total  solids  is  made  by 
evaporating  loo  c.c.  of  the  water  in  the  platinum 
basin,  which  has  been  previously  heated  almost  to 
redness,  allowed  to  cool  for  ten  minutes,  and 
weighed.  The  operation  is  conducted  at  a  moder- 
ate heat. 

When  the  residue  appears  dry,  the  heat  may  be 
increased  slightly  for  some  minutes.  The  above 
method  will  answer  in  most  cases.     In  waters  of 


l8  ANALYTIC    OPERATIONS. 

exceptional  purity  it  may  be  advisable  to  use 
larger  quantities,  such  as  250  c.c.  When  the 
residue  contains  deliquescent  bodies,  the  deter- 
mination will  not  be  accurate,  and  when  appre- 
ciable amounts  of  magnesium  and  chlorin  are 
present,  a  decomposition  will  occur  by  which 
magnesium  oxid  will  be  formed  and  hydrogen 
chlorid  escape. 

Deliquescence  of  residues  and  decomposition 
during  evaporation  may  be  largely  prevented  by 
adding  0.005  gram  of  sodium  carbonate  to  each 
100  c.c.  of  the  sample  taken.  This  converts 
magnesium  and  calcium  salts  into  carbonates. 
The  sodium  carbonate  is  conveniently  kept  in  the 
form  of  solution  of  such  strength  that  i  c.c.  con- 
tains 0.00 1  gram.  The  weight  of  the  carbonate 
is,  of  course,  to  be  deducted  from  the  weight  of  the 
residue.  Drown  and  Hazen  have  carefully  in- 
vestigated this  method  and  have  found  it  available 
for  a  more  satisfactory  determination  of  the  loss  on 
ignition.  For  this  process  a  thin-walled  platinum 
basin  is  placed  within  another  similar  basin  of  such 
size  that  an  air-space  of  about  one-half  of  an  inch 
is  left  all  around  the  inner  dish,  which  is  supported 
upon  a  spiral  of  platinum  that  rests  on  the  bottom 
of  the  outer  dish.  Over  the  inner  dish  is  sus- 
pended a  disc  of  platinum  foil  to  reflect  the  heat. 
The  outer  dish  is  heated  to  bright  redness. 

After  the  weight  of  the  residue   is  obtained, 


SANITARY    EXAMINATIONS.  I9 

many  chemists  heat  the  dish  cautiously  to  low 
redness,  and  note  the  effect.  Nitrates  and  ni- 
trites, calcium  and  magnesium  carbonates,  are  de- 
composed; ammonium  salts  are  driven  off; 
potassium  and  sodium  chlorids  are  also  driven  off 
if  the  temperature  is  high.  Organic  matter  is  at 
first  charred,  and  by  continued  heating  burned 
off.  When  the  quantity  of  nitrates  is  considerable, 
slight  deflagration  may  be  observed,  or  the  pro- 
duction of  red  fumes  of  nitrogen  dioxid.  The 
organic  matter,  in  decomposing,  not  infrequently 
develops  odors  which  indicate  its  character  or 
source.  These  are  more  satisfactorily  observed 
when  a  rather  large  quantity,  say  250  c.c,  is  evap- 
orated at  a  low  heat,  preferably  on  a  water-bath. 

In  water  of  high  organic  purity,  the  residue  on 
heating  will  give  no  appreciable  blackening  nor 
odor,  while  in  forest  streams  charged  with  vege- 
table matter  derived  from  falling  leaves,  very 
decided  blackening  without  unpleasant  odor  will 
be  noticed.  The  loss  on  heating  can  not  be  taken 
as  a  measure  of  the  organic  matter,  except  when 
present  in  relatively  large  amount.  The  difference 
between  the  weight  before  and  after  heating  is 
often  reported  as  ''organic  and  volatile  matter" 
but  it  has  rarely  any  practical  value. 

In  many  cases  the  determination  of  total  solids, 
being  merely  for  control,  may  be  made  in  glass 
dishes.     I    have    found   especially   convenient    a 


20  ANALYTIC    OPERATIONS. 

shallow  dish  made  by  cutting  off  a  beaker  about 
8  centimeters  in  diameter,  so  as  leave  a  depth  of 
about  3  centimeters.  The  cutting  can  be  easily 
done  by  the  use  of  a  hot  iron,  and  the  edge 
can  be  ground  with  carborundum  or  emery  on  an 
iron  or  glass  plate.  A  dish  of  the  above  dimen- 
sions will  hold  ICG  c.c.  It  is  most  safely  heated  by 
placing  it  on  a  piece  of  wire  gauze  which  rests 
upon  the  flanges  of  the  low  temperature  burner. 
The  gas  should  be  turned  so  as  to  give  a  ring  of 
flames  not  over  i  centimeter  high.  The  dish 
should  be  warmed,  allowed  to  cool,  and  weighed, 
and  ICG  c.c.  of  the  water  put  in.  After  the  residue 
has  been  weighed,  it  may  be  removed  by  addition 
of  a  little  strong  hydrochloric  acid  with  strong 
rubbing  with  a  rubber-tipped  rod.  Of  course, 
the  determination  of  volatile  matter  by  heating  to 
redness  cannot  be  made,  but  this  is  of  no  value  in 
the  ordinary  sanitary  and  technic  examinations. 
I  have  found  that  a  dish  made  from  a  good  quality 
of  glass  weighs  about  25  grams  and  loses  little  by 
use. 

In  connection  with  the  determination  of  the 
total  solids,  two  qualitative  tests  should  be  made. 
Separate  portions  of  the  sample  should  be  tested 
with  ammonium  oxalate  and  barium  chlorid.  If  a 
precipitate  is  produced  by  the  latter  reagent,  a 
few  drops  of  hydrochloric  should  be  added.  A 
permanent    precipitate    shows    sulfates.     If    the 


SANITARY    EXAMINATIONS.  21 

precipitate  disappears,  it  was  probably  carbonate. 
A  precipitate  with  ammonium  oxalate  shows 
calcium  compounds.  As  a  rule,  if  a  notable 
amount  of  either  calcium  or  magnesium  car- 
bonate is  present,  a  crystalline  scum  forms  during 
evaporation.  The  residue  effervesces  actively  with 
hydrochloric  acid. 


CHLORIN. 
Solutions  Required : 

Standard  Silver  Nitrate. — Five  grams  of  pure 
recrystallized  silver  nitrate  are  dissolved  in  dis- 
tilled water,  and  the  solution  made  up  to  looo  c.c. 
The  amount  of  chlorin  to  which  this  is  equivalent 
may  be  determined  as  follows:  Several  grams  of 
pure  sodium  chlorid  are  finely  powdered  and 
heated  for  five  minutes,  not  quite  to  redness. 
When  cold,  0.824  gram  are  dissolved  in  water  and 
the  solution  made  up  to  500  c.c.  Twenty-five  c.c. 
of  this  should  be  treated  as  below,  and  the  amount 
of  silver  solution  required  noted.  Each  c.c.  of  the 
sodium  chlorid  solution  is  equivalent  to  0.00 1 
gram  chlorin. 

Potassium  Chromate. — Five  grams  of  potassium 
chromate  are  dissolved  in  100  c.c.  of  distilled 
water.  Absolution  of  silver  nitrate  is  added  until  a 
permanent  red  precipitate  is  produced,  which  is 
separated  by  filtration. 


2  2  ANALYTIC    OPERATIONS. 

Analytic  Process : 

If  a  preliminary  test  shows  the  chlorin  to  be 
present  in  considerable  amount,  the  determination 
may  be  made  on  loo  c.c.  of  the  water  without  con- 
centration. If,  however,  there  is  but  little  present, 
250  c.c.  should  be  evaporated  to  about  one-fifth, 
best  with  the  addition  of  a  little  sodium  carbonate, 
and  the  determination  made  on  the  concentrated 
liquid  after  cooling. 

The  water  is  placed  in  a  porcelain  dish  or  in  a 
beaker  standing  on  a  white  surface,  a  few  drops  of 
potassium  chromate  solution  added,  and  standard 
silver  nitrate  solution  run  in  from  a  buret  until  a 
faint  red  color  of  silver  chromate  remains  per- 
manent on  stirring.  The  proportion  of  chlorin  is 
then  calculated  from  the  number  of  c.c.  of  silver 
solution  added.  Greater  accuracy  is  secured  by 
operating  in  yellow  light.  A  second  determination 
may  be  made,  using  as  a  comparison  the  liquid 
first  titrated,  the  red  color  having  been  previously 
discharged  by  a  few  drops  of  sodium  chlorid  solu- 
tion. 

The  water  should  always  be  as  nearly  neutral 
as  possible  before  titration.  If  acid,  it  may  be 
neutralized  by  the  addition  of  sodium  carbonate. 

The  residue  obtained  by  evaporating  the  water 
with  sodium  carbonate,  as  described  in  connection 
with  the  determination  of  the  total  solids,  will 
often    serve     conveniently    for    estimating    the 


I 


SANITARY   EXAMINATIONS.  2^ 


chlorin.  It  is  best  to  use  200  c.c.  of  the  sample 
and  redissolve  the  residue  in  about  50  c.c.  of  dis- 
tilled water,  rubbing  the  sides  of  the  dish  well  with 
a  rubber-tipped  rod,  and  then  titrating  as  indicated 
above. 


NITROGEN    IN    AMMONIUM    COMPOUNDS 
AND  IN  ORGANIC  MATTER. 

Determinations  of  these  data  are  usually  carried 
out  as  one  operation,  known  as  the  **  ammonia 
method."  The  originators,  Wanklyn,  Chapman 
and  Smith,  applied  the  term  ''free  ammonia"  to 
the  ammonium  compound  obtained  by  the  distilla- 
tion of  the  sample  with  sodium  carbonate,  and  the 
term  ''albuminoid  ammonia"  to  that  obtained  by 
distilling  the  sample  with  a  strongly  alkaline  solu- 
tion of  potassium  permanganate  (alkaline  per- 
manganate). Both  terms  are  somewhat  objec- 
tionable, and  in  this  book  the  former  will  be  sub- 
stituted by  "nitrogen  as  ammonium"  and  the 
latter  by  "nitrogen  by  permanganate." 
Apparatus  Required : 

Distilling  Apparatus. — That  shown  in  figure  3 
is  convenient.  The  still  consists  of  a  glass  retort 
of  about  1000  c.c.  capacity.  The  beak  of  the 
retort  should  incline  slightly  upward,  to  prevent 
contamination  by  splashing.  At  about  seven 
centimeters  from  the  end  it  should  be  bent  at  a 


24 


ANALYTIC    OPERATIONS. 


right  angle,  and  drawn  out  so  as  to  enter  the  con- 
densing worm  for  such  a  distance  as  to  terminate 
beneath  the  level  of  the  water. 

The  condenser  shown  in  figure  3   is  a  copper 
tank,  33  cm.  high,  15  cm.  wide,  and  of  length  pro- 


FlG.  3- 


portioned  to  the  number  of  distilling  vessels 
operated.  The  condensing  tube  is  not  shown  in 
its  course  thru  the  tank. 

Glass  worms  are  apt  to  break,  and  it  is  more 
satisfactory  to  use  block  tin.     A  piece  of  rubber 


SANITARY    EXAMINATIONS.  25 

tubing  is  drawn  over  the  junction  between  the 
retort  neck  and  worm.  A  rapid  current  of  cold 
water  should  be  maintained  through  the  con- 
denser. The  heat  is  applied  by  means  of  the  low- 
temperature  burner,  the  iron  ring  of  which  is  re- 
moved so  that  the  retort  rests  directly  on  the 
gauze. 

To  prevent  overheating  of  the  upper  part  of  the 
retort,  a  sheet  of  thick  asbestos  board,  about  20 
cm.  in  diameter,  with  a  central  opening  about 
5  cm.  in  diameter,  may  be  placed  on  the  gauze. 
With  this  arrangement  the  heat  is  under  control, 
and  the  danger  of  breaking  the  retort  is  slight. 
It  is  advisable  to  protect  the  retort  from  drafts 
of  cold  air,  which  may  be  done  with  a  cone  made 
of  thin  sheet  asbestos. 

Many  liquids,  boiling  percussively,  are  liable 
to  break  glass  vessels.  Among  the  most  success- 
ful methods  for  preventing  this  is  the  introduction 
of  a  few  fragments  of  pumice.  Common  pumice 
is  broken  into  masses  about  as  large  as  an  olive- 
stone,  which  are  placed  in  a  flask  or  bottle,  filled 
with  water,  and  corked.  In  a  few  days  the  frag- 
ments will  have  become  waterlogged  and  sink. 
If  it  is  necessary  to  bring  some  fragments  to  this 
condition  at  short  notice,  it  may  be  done  by 
heating  them  to  redness  and  quenching  in  cold 
water.  Two  or  three  waterlogged  fragments 
should  be  put  into  each  distilling  flask.     They 


26 


ANALYTIC    OPERATIONS. 


will  serve  for  several  operations,  but  must  be 
occasionally  renewed.  The  stock  of  fragments 
should  be  kept  in  a  bottle  filled  with  water. 

Fig.   4  shows  a  distilling  arrangement,  which 


Fig.  4. 


is  convenient  for  many  laboratory  purposes.  The 
condenser  shown  is  relatively  too  short.  It  should 
be  not  less  than  50  centimeters  long.  It  is  ad- 
visable to  use  Jena  glass  for  the  inner  tube.  The 
side-tube  should  be  at  such  an  angle  as  will  permit 


SANITARY    EXAMINATIONS.  2^ 

of  the  flask  being  upright  when  the  condenser  has 
the  proper  angle.  The  thermometer  shown  in 
the  cut  is,  of  course,  unnecessary  in  the  process 
under  consideration.  The  flask  should  be  closed 
by  a  rubber  stopper.  All  materials  should  be  in- 
troduced by  the  aid  of  a  long-necked  funnel,  so 
that  no  splashing  occurs.  This  funnel  should  be 
well  rinsed  before  use.  The  side  tube  should  be 
pushed  into  the  condensing  tube  so  that  its  end  will 
be  well  within  the  cooled  portion  of  the  condensing 
tube.  The  junction  can  be  made  tight  by  slipping 
a  short  piece  of  rubber  over  the  condenser  tube 
and  passing  the  side-tube  of  the  flask  thru. 

Another  convenient  form  of  apparatus  is  shown 
in  figure  5.  It  is  employed  in  the  laboratory  of 
the  Massachusetts  State  Board  of  Health.  The 
joint  between  the  flask  and  condenser  is  made  by 
means  of  a  sound  cork,  into  which  the  condensing 
tube  fits  closely ;  the  tube  from  the  flask  is  made 
slightly  smaller  than  the  condensing  tube,  and 
passes  into  it  for  about  four  centimeters. 

A  form  of  condenser  applicable  to  distillations  of 
this  character  has  been  devised  by  Cribb  and  is 
shown  in  figure  6.  The  vapor  passes  into  a  narrow 
annulus  by  the  tube  A;  the  cooling  water  enters 
the  central  portion  and  overflows,  running  down 
the  outside  wall,  being  collected  by  the  projecting 
rim  and  carried  off  by  the  tube  G.  For  water 
analysis  a  retort  with  the  neck  bent,  about  the 


28 


ANALYTIC   OPERATIONS. 


middle,  at  an  obtuse  angle,  may  be  used,  or  a 
flask  with  side-tube.     In  the  latter  case  the   tube 


Scale  m  \n.=  i  foot. 

Fig.  s. 


must  leave  the  flask  at  a  slight  angle  upward,  and 
about  midway  be  bent  at  a  slight  obtuse  angle 
downward.     This  prevents  contamination  of  the 


I 


SANITARY    EXAMINATIONS. 


29 


D 


D 


distillate  by  spurting.  The  drawing  shows  the 
form  given  by  Cribb,  but  experience  has  shown 
that  more  space  should  be  allowed  between  the 
inner  and  outer  wall  at  the  lowest  point,  and  that 
the  catch-basin  should  be  large.  The  tube,  G, 
should  be  at  least  three  times  the  caliber  of  F. 
It  will  often  be  advantageous 
to  wrap  a  piece  of  muslin 
around  the  body  of  the  ap- 
paratus. 

A  modified  form  of  this 
apparatus  is  now  sold  as 
''Hopkins,  Condenser." 

Cylinders  for  Comparison- 
color  Tests,  usually  called 
*'Nessler  glasses."  They 
should  be  made  of  colorless 
glass,  be  about  2.5  centimeters 
in  diameter,  and  marked  at 
SO  c.c. 
Solutions  Required : 

Ammonium-free  Water. — If 
the  distilled  water  of  the 
laboratory  gives  a  reaction 
with  Nessler  reagent,  it  should  be  treated  with 
sodium  carbonate,  about  one  grain  to  the  liter, 
and  boiled  until  about  one-fourth  has  been 
evaporated.  Ammonium-free  water  may  be  ob- 
tained by  distilling,  in  a  retort,  water  made  slightly 
acid  with  sulfuric  acid. 


Fig.  6. 


30  ANALYTIC    OPERATION^. 

Messrs.  J.  B.  Weems,  C.  E.  Gray,  and  E.  C. 
Myers  recommend  the  following  method :  Sodium 
dioxid  is  added  to  ordinary  water  in  the  proportion 
of  one  gram  to  a  liter,  and  the  liquid  boiled  for 
thirty  minutes,  or  longer  if  the  amount  of  am- 
monium compounds  is  high.  It  is  then  cooled 
and  the  flask  kept  closed.  Flasks  holding  several 
liters  are  most  convenient.  If  the  water  be  dis- 
tilled, the  distillate  may  also  be  used  for  the  pre- 
paration of  standard  nitrate  and  nitrite  solutions. 
Standard  Ammonium  Chlorid. — Dis- 
solve 0.382  gram  of  pure  dry  ammonium 
chlorid  in  100  c.c.  of  ammonium-free 
water.  For  use,  dilute  i  c.c.  of  this 
solution  with  pure  .water  to  100  c.c. 
One  c.c.  of  this  dilute  solution  contains 
0.0000 1  gram  of  nitrogen. 
Fig.  7.  Nessler  Reagent. — Dissolve  17.5  grams 

of  potassium  iodid  in  50  c.c.  of  water. 
Dissolve  8  grams  of  mercuric  chlorid  in  200  c.c.  of 
water.  The  liquids  may  be  heated  to  aid  solution, 
but  must  be  cooled  before  use.  Add  the  mercuric 
chlorid  solution  to  that  of  the  potassium  iodid, 
until  a  permanent  precipitate  is  produced.  Then 
dilute  with  a  20  per  cent,  solution  of  sodium 
hydroxid  to  500  c.c,  add  mercuric  chlorid  solution 
until  a  permanent  precipitate  again  forms,  and 
allow  to  stand  until  clear.  Nessler  and  other 
reagents  are   best    kept  in   glass-capped    bottles 


SANITARY    EXAMINATIONS.  3 1 

(Fig.  7)  for  water  analysis,  in  which  the  pipet 
may  remain  when  not  in  use. 

A  Ikaline  Potassium  Permanganate. — Dissolve 
200  grams  of  potassium  hydroxid,  in  sticks,  and 
8  grams  of  potassium  permanganate,  in  looo  c.c. 
of  distilled  water.  It  was  originally  recommended 
to  boil  this  solution  for  some  time  to  remove  am- 
monium, but  the  procedure  described  in  the  next 
paragraph  renders  this  preliminary  treatment 
unnecessary. 

The  Chemical  Section  of  the  American  Associa- 
tion for  the  Advancement  of  Science  recommended 
the  following  method,  which  is  very  satisfactory: 

200  c.c.  of  distilled  water,  and  about  i  gram  of 
pure  sodium  carbonate,  are  distilled  down  to 
about  100  c.c.  in  the  retort  in  which  the  analysis 
is  to  be  conducted,  and  the  last  portion  of  50  c.c. 
nesslerized  to  assure  freedom  from  ammonium. 
Then  500  c.c.  of  the  water  to  be  examined  are 
added,  and  the  distillation  is  carried  on  at  such  a 
rate  that  about  50  c.c.  are  collected  in  each  suc- 
ceeding ten  minutes,  and  until  a  50  c.c.  measure 
of  distillate  is  obtained  containing  only  an  in- 
appreciable quantity  of  ammonium.  In  nessler- 
izing,  five  minutes  are  to  be  allowed  for  the  full 
development  of  color ;  after  this,  no  change  takes 
place  for  many  hours. 

The  distilling  vessel  is  emptied  and  rinsed  thor- 
oughly, 200  c.c.  of  distilled  water  and  50  c.c.  of 


^2  ANALYTIC    OPERATIONS. 

alkaline  permanganate  solution  put  in,  and  the 
liquid  distilled  down  to  about  loo  c.c.,  the  last 
portions  of  the  distillate  being  tested  to  ascertain 
freedom  from  ammonium  compounds,  another 
portion  of  500  c.c.  of  the  water  to  be  tested  is 
added,  and  the  distillation  made  as  before.  The 
difference  between  the  ''nitrogen  as  ammonium" 
C'free  ammonia")  of  the  first  operation  and  the 
total  ammonia  of  the  second  is  to  be  taken  as  the 
''nitrogen  by  permanganate"  ("albuminoid  am- 
monia"). 

It  is  convenient  to  operate  the  distilling  flasks 
in  pairs,  using  one  of  each  pair  for  the  perman- 
ganate process.  Delay  and  trouble  of  rinsing  are 
thus  avoided.  Before  beginning  an  analysis,  the 
greater  part  of  the  residues  from  a  previous 
operation  may  be  drawn  off  from  the  flasks  with  a 
siphon,  200  c.c.  of  distilled  water  added  to  each, 
and  the  liquids  distilled  until  the  reagent  shows 
freedom  from  ammonium  compounds.  Suitable 
portions  of  the  sample  are  then  put  in  each  flask. 

"Nesslerizing,"  the  term  applied  to  the  use  of 
Nessler's  reagent  for  determining  the  ammonium 
in  the  distillates,  is  performed  as  follows:  To 
each  of  the  distillates  of  50  c.c.  collected,  as 
directed,  in  the  comparison  cylinders,  or  other 
suitable  vessels,  2  c.c.  of  Nessler's  reagent  are 
added.  A  yellowish-brown  solution  is  formed, 
the  intensity  of  which  is  proportional  to  the  amount 


SANITARY    EXAMINATIONS.  ;^^ 

of  ammonium  present.  The  full  color  is  de- 
veloped in  five  minutes.  This  color  is  exactly 
matched  by  introducing  into  another  cylinder  50 
c.c.  of  ammonium-free  water,  some  of  the  standard 
ammonium  chlorid  solution,  and  2  c.c.  Nessler 
reagent  as  before.  According  as  the  color  so 
produced  is  deeper  or  lighter  than  that  obtained 
from  the  water,  other  comparison  liquids  are  pre- 
pared containing  smaller  or  larger  proportions  of 
the  ammonium  chlorid,  until  the  proper  color  is 
produced. 

If  the  quantity  of  ammonium  is  sufficient  to 
cause  a  precipitate,  the  color  comparison  can  not 
be  accurately  made.  In  most  cases  this  will  not 
be  of  serious  moment,  as  the  quantity  will  be 
"beyond  the  allowable  limit.  If  accurate  deter- 
mination be  desired,  it  may  be  made  by  dividing 
the  first  distillate  into  two  equal  parts,  nessleriz- 
ing  one  of  these,  and  then,  if  necessary,  diluting 
the  second  part  with  ammonium-free  water  and 
nesslerizing  this. 

Since  small  quantities  of  ammonium  compounds 
and  nitrogenous  matters  are  everywhere  present, 
the  greatest  care  should  be  exercised  in  order  to 
avoid  their  introduction  in  any  way  during  the 
course  of  the  analysis.  All  measuring  vessels, 
cylinders,  pipets,  and  flasks,  etc.,  should  be  thor- 
oughly rinsed  before  using.  The  temperatures 
of  the  distillates  and  standards  should  be  ap- 
3 


34 


ANALYTIC    OPERATIONS. 


proximately  the  same  when  the  colors  are  com- 
pared. 

For  nesslerizing  and  other  color  comparisons, 
many  forms  of  apparatus  have  been  proposed. 
One,  devised  by  Hehner, 
is  shown  in  figure  8.  It 
consists  of  a  graduated 
cylinder  with  a  stopcock 
near  the  base,  by  which 
the  liquid  can  be  drawn 
down  at  will.  Two  such 
cylinders  may  be  used — 
one  for  the  nesslerized  dis- 
tillate, the  other  for  the 
comparison   liquid.     The 


/N 


5ftcc. 


Uco 


Sl6c 


3Y^ 


<|Xi> 


Fig.  8. 


Fig.  9. 


darker  liquid  is  drawn  out  until  the  tints  are 
equal,  when  the  relative  volumes  remaining  will 
give  the  data  for  calculation. 

H.  J.  Watson  has  modified  the  Hehner  tube  as 


SA*nTARY    EXAMINATIONS. 


35 


shown  in  figures  9  and  10.     The  cuts  were  loaned 
by  the  Amer.  Jour,  of  Pharmacy.     The  jar  is   30 


Fig.  10. 


cm.  long,  1.8  cm.  in  diameter,  and  is  graduated 
into  cubic  centimeters  for  about  20  cm.  from  the 
base.     At  the  side  of  the  base  a  small  tube  pro- 


36  ANALYTIC    OPERATIONS. 

jects,  which  may  be  provided  with  a  stop-cock, 
but  it  will  be  seen  from  one  of  the  figures  that  this 
is  not  necessary.  A  number  of  tubes  similar  in  size 
and  quality  of  glass  to  the  graduated  tube,  but 
marked  only  at  50  c.c,  should  be  provided.  The 
distillates  from  the  water  are  placed  in  the  un- 
graduated  tubes,  and  compared  with  the  tints  of 
the  standard  ammonium  solution,  by  making  the 
volume  of  the  latter  in  the  graduated  tube  increase 
or  decrease  by  means  of  the  stop-cock  on  the 
buret  and  changing  the  height  of  the  latter. 


TOTAL  ORGANIC  NITROGEN. 

The  ease  and  certainty  with  which  the  nitrogen 
of  most  organic  bodies  may  be  converted  into 
ammonium  sulfate .  by  boiling  with  sulfuric  acid 
offers  a  means  of  determination  free  from  the' ob- 
jections of  former  methods.  The  method  in- 
troduced by  Kjeldahl  for  general  organic  analysis 
was  first  successfully  applied  to  water  analysis  by 
Drown  and  Martin. 

In  their  original  process,  500  c.c.  was  concen- 
trated to  about  300  c.c,  and  the  distillate  nessler- 
ized  for  determining  the  nitrogen  existing  as 
ammonium  compounds.  The  organic  nitrogen  is 
then  determined  in  the  residual  water.  Owing 
to  the  fact  that  organic  matter  may  be  decom- 
posed by  moderate  heat,  there  is  liability  to  under- 


■fIT 


SANITARY   EXAMINATIONS.  37 

estimation  of  the  nitrogen.  It  is  best,  therefore, 
to  determine  at  once  the  total  unoxidized  nitrogen, 
and  estimate,  without  distillation,  on  a  separate 
portion  of  the  sample,  the  nitrogen  that  exists  in 
ammonium  compounds.  The  procedure  is  as 
follows : 
Reagents  Required : 

Concentrated  Sulfuric  Acid. — This  should  be  as 
free  as  possible  from  nitrogen.  ,  It  can  now  be 
obtained  of  high  purity. 

Sodium  Hydroxid  Solution. — The  white  granu- 
lated caustic  soda  sold  for  household  use  will 
answer;  350  grams  are  dissolved  in  water  and 
made  up  to  1000  c.c. 

Sodium    Carbonate    and  Hydroxid    Solution. — 
Twenty-five  grams  of  each  are  dissolved  in  250  c.c. 
of  distilled  water,  and  the  solution  boiled  down  to 
200  c.c.  to  free  it  from  ammonium. 
Analytic  Process : 

Determination  of  Nitrogen  Existing  as  Am- 
monium.— Two  hundred  c.c.  of  the  water  are 
placed  in  a  stoppered  bottle,  two  c.c.  each  of  the 
solutions  of  sodium  carbonate  and  sodium  hy- 
droxid added,  the  stopper  inserted,  the  solutions 
mixed,  and  allowed  to  stand  for  an  hour  or  two. 
A  filter  is  prepared  by  inserting  a  rather  large  plug 
of  absorbent  cotton  in  a  funnel.  This  should  be 
washed  with  ammonium-free  water  until  the 
filtrate  gives  no  color  with  Nessler  reagent.     The 


YliAlllilJ 

38  ANALYTIC    OPERATIONS. 

clear  portion  of  the  sample  is  drawn  off  with  a 
pipet  and  run  thru  the  filter,  the  first  portions 
being  rejected,  since  it  is  diluted  by  the  water 
retained  in  the  cotton.  The  filtration  is  rapid,  and 
when  100  c.c.  of  the  liquid  have  passed  thru  it,  is 
nesslerized.  If  but  little  ammonium  is  present, 
a  narrow  tube  about  60  centimeters  long  should  be 
used  for  observing  the  color. 

Estimation  of  the  Total  Organic  and  Ammoniac al 
Nitrogen. — Five  hundred  c.c.  of  the  water  are 
placed  in  a  round-bottomed  Jena  glass  flask,  10 
c.c.  of  concentrated  sulfuric  acid  added,  and  a 
piece  of  pumice-stone  is  heated  to  bright  redness 
and  dropped  in  while  hot.  The  liquid  is  boiled  for 
an  hour  after  it  is  colorless,  or,  at  least,  very  pale 
yellow.  The  flask  is  allowed  to  cool,  and  about 
250  c.c.  of  ammonium-free  water  added.  Fifty 
c.c.  of  the  sodium  hydroxid  solution  should  be 
placed  in  the  distilling  apparatus,  about  250  c.c. 
of  water  added,  a  piece  of  red-hot  pumice-stone 
dropped  in,  and  the  liquid  distilled  until  the  dis- 
tillate is  free  from  ammonium.  It  is  best  to  distil 
until  the  retort  contains  not  more  than  100  c.c. 
The  sulfuric  acid  solution  is  then  poured  in  slowly 
by  means  of  a  funnel,  the  stem  of  which  touches 
the  side  of  the  retort,  so  that  the  two  liquids  do  not 
mingle.  The  stopper  of  the  retort  is  inserted,  the 
liquids  mixed  by  gentle  agitation,  and  distilled. 
If  much  ammonium  is  present,  it  is  advisable  to 


I 


SANITARY    EXAMINATIONS.  39 


distil  the  first  portion  into  10  c.c.  of  very  dilute 
(i  :  1000)  sulfuric  acid,  a  piece  of  glass  tube  being 
connected  to  the  condensing  worm,  so  that  the 
lower  end  dips  below  the  surface  of  the  liquid. 
The  distillates  are  collected  and  nesslerized  in  the 
usual  way. 

A  blank  experiment  should  be  made  to  deter- 
mine the  amount  of  ammonium  in  the  sulfuric  acid. 

NITROGEN  AS  NITRATES. 

A.  H.  Gill  has  subjected  the    various  indirect 
methods   of  estimating  nitrates   to   comparative 
examination,    and    finds    the    following    method 
satisfactory : 
Solutions  Required : 

Phenoldisulfonic  Acid: 

Sulfuric  acid iii  grams. 

Phenol 9       " 

The  mixture  is  heated  for  six  hours  in,  not 
upon,  the  water-bath.  The  resulting  compound 
often  solidifies  to  a  white  mass  on  standing,  but 
can  be  easily  liquefied  on  the  water-bath  during 
the  evaporation  of  the  samples  to  be  tested. 

Standard  Potassium  Nitrate. — 0.722  gram  of 
potassium  nitrate,  previously  heated  to  a  tem- 
perature just  sufficient  to  fuse  it,  dissolved  in 
water,  and  the  solution  made  up  to  looo  c.c.     One 


40  ANALYTIC    OPERATIONS. 

c.c.  of  this  solution  will  contain  o.oooi  gram  of 

nitrogen. 

Analytic  Process : 

A  measured  volume  of  the  water  is  evaporated 
just  to  dryness  in  a  porcelain  basin  about  six 
centimeters  in  diameter.  One  c.c.  of  the  -phenol- 
disulfonic  acid  is  added  and  thoroughly  mixed 
with  the  residue  by  means  of  a  glass  rod.  The 
liquid  is  then  diluted  with  about  25  c.c.  of  water, 
ammonium  hydroxid  added  in  excess,  and  the 
solution  made  up  to  50  c.c. 

The  nitrate  converts  the  phenoldisulfonic  acid 
into  picric  acid,  which,  by  the  action  of  the  am- 
monium hydroxid,  forms  ammonium  pier  ate ;  this 
imparts  to  the  solution  a  yellow  color,  the  intensity 
of  which  is  proportional  to  the  amount  present. 

One  c.c.  of  the  standard  solution  of  potassium 
nitrate  is  now  similarly  evaporated  in  a  platinum 
basin,  treated  as  above,  and  made  up  to  50  c.c. 
The  color  produced  is  compared  to  that  given  by 
the  water,  and  one  or  the  other  of  the  solutions  is 
diluted  until  the  tints  of  the  two  agree.  The 
comparative  volumes  of  the  liquids  furnish  the 
necessary  data  for  determining  the  amount  of 
nitrate. 

The  results  obtained  by  this  method  are  satis- 
factory. Care  should  be  taken  that  the  same 
quantities  of  phenoldisulfonic  acid  are  used  for  the 
water  and  for  the  comparison  liquid. 


SANITARY    EXAMINATIONS.  41 

With  subsoil  and  other  waters  probably  con- 
taining much  nitrates,  lo  c.c.  will  be  sufficient; 
but  with  river  and  spring  waters,  25  c.c.  may  be 
used.  When  the  organic  matter  is  sufficient  to 
color  the  residue,  it  will  be  well  to  purify  the  water 
by  addition  of  aluminum  hydroxid  and  filtration, 
before  evaporating. 

Chlorin  interferes  with  the  accuracy  of  the  test, 
but  Gill  finds  that  when  not  amounting  to  more 
than  20  parts  per  million,  it  does  not  impair  the 
practical  value  of  the  results.  When  greater  than 
this,  it  is  best  to  evaporate  in  vacuo  over  sulfuric 
acid.  If  the  chlorin  is  more  than  70  parts  per 
million,  it  should  be  considerably  reduced  by  the 
addition  of  silver  sulfate  which  has  been  ascer- 
tained to  be  free  from  nitrates.  Nitrites  do  not 
influence  the  reaction. 

Nitron  Method. — A  complex  synthetic  product, 
the  cumbersome  systematic  name  of  which  has 
been  replaced  by  the  commercial  name  ** nitron," 
forms  with  nitric  acid  a  definite  compound  spar- 
ingly soluble  in  cold  water.  The  application  of 
this  substance  is  more  likely  to  be  made  in  the 
general  assay  of  nitrates,  but  as  it  may  have  oc- 
casional application  in  water  analysis,  the  analytic 
method  is  briefly  described. 

Nitron  is  a  yellowish  powder.  For  use  it  is 
dissolved  in  the  proportion  of  i  gram  to  loo  c.c. 
of  5  %  acetic  acid.     The  solution  does  not  keep 


42  ANALYTIC    OPERATIONS. 

long,  hence  large  amounts  should  not  be  made  up 
at  once.  The  determination  is  made  by  adding 
to  a  convenient  amount  of  the  solution  of  the 
nitrate,  sufficient  dilute  sulfuric  acid  to  make  the 
liquid  distinctly  acid,  heating  to  boiling,  adding 
a  few  c.c.  of  the  nitron  solution,  and  then  allowing 
the  liquid  to  cool  to  room  temperature,  after 
which  it  is  immersed  in  melting  ice  for  several 
hours.  Max  Busch,  to  whom  the  discovery  of 
the  use  of  nitron  is  due,  states  that  the  substances 
usually  occurring  in  water  do  not  interfere,  and 
that  the  reagent  will  give  a  precipitate  with  i 
part  of  nitric  acid  in  60,000  of  water.  This  cor- 
responds to  about  4  parts  of  nitrogen  per  1,000,000. 
The  precipitate  must  be  collected  on  a  filter, 
preferably  by  means  of  the  gooch  crucible,  well 
sucked  out  by  the  filter  pump,  washed  with  a  few 
c.c.  of  water  as  near  0°  as  possible,  again  sucked 
out,  dried  and  weighed.  The  weight  multiplied 
by  0.037  gives  nitrogen. 

Concentration  of  water  samples  will,  of  course, 
increase  the  delicacy  of  the  test.  This  concen- 
tration should  be  carried  on  at  a  very  low  tem- 
perature, and  the  water  should  be  neutral  or 
alkaline,  or  nitrates  will  be  decomposed. 

NITROGEN  AS  NITRITES. 

The    following    is     Ilosvay's    modification    of 

Griess's   test.     It   has   the    advantage    over   the 


SANITARY    EXAMINATIONS.  43 

original  method,  that  the  color  is  developed  more 
rapidly,  and  the  solutions  are  less  liable  to  change. 
Solutions  Required : 

.  1-4-Amidobenzenesulfonic  Acid  Solution  (Sulf- 
anilic  Acid). — 0.5  gram  dissolved  in  150  c.c.  of 
diluted  acetic  acid,  sp.  gr.  1.04. 

a-Amidonaphthalene  Acetate  Solution. — Boil  o.i 
gram  of  solid  a-amidonaphthalene  (<3t-naphthyl- 
amin)  in  20  c.c.  of  water,  filter  the  solution  thru 
a  plug  of  washed  absorbent  cotton,  and  mix  the 
filtrate  with  180  c.c.  of  diluted  acetic  acid.  All 
water  used  must  be  free  from  nitrites,  and  all 
vessels  must  be  rinsed  out  with  such  water  before 
tests  are  applied,  since  appreciable  quantities  of 
nitrites  may  be  taken  up  from  the  air. 

Much  of  the  commercial  «-naphthylamin  has  a 
very  offensive  odor,  but  a  pure  article  less  ob- 
jectionable can  now  be  obtained. 

Standard  Sodium  Nitrite. —  0.275  gram  pure 
silver  nitrite  dissolved  in  pure  water,  and  mixed 
with  a  dilute  solution  of  pure  sodium  chlorid  until 
a  precipitate  ceases  to  form.  The  solution  is 
diluted  with  pure  water  to  250  c.c,  and  allowed  to 
stand  until  clear.  For  use  10  c.c.  of  this  solution 
are  diluted  to  100  c.c.  It  is  to  be  kept  in  the  dark. 
One  c.c.  of  the  dilute  solution  is  equivalent  to 
0.00001  gram  nitrogen. 

The  silver  nitrite  is  prepared  thus:  A  hot  con- 
centrated solution  of  silver  nitrate  is  added  to  a 


1% 


44  ANALYTIC    OPERATIONS. 

concentrated  solution  of  the  purest  sodium  or 
potassium  nitrite  available,  filtered  while  hot,  and 
allowed  to  cool.  The  silver  nitrite  will  separate  in 
fine,  needle-like  crystals,  which  are  freed  from  the 
mother  liquor  by  filtration  by  the  aid  of  a  filter 
pump.  The  crystals  are  dissolved  in  the  smallest 
possible  quantity  of  hot  water,  allowed  to  cool, 
and  again  separated  by  means  of  the  pump. 
They  are  then  thoroly  dried  in  the  water-bath,  and 
preserved  in  a  tightly  stoppered  bottle  away  from 
the  light.  The  purity  may  be  tested  by  heating  a 
weighed  quantity  to  redness  in  a  tared  porcelain 
crucible.  The  residue  is  silver  and  should  be 
70.1%  of  the  weight  of  nitrite  taken. 
Analytic  Process : 

Twenty-five  c.c.  of  the  water  are  placed  in  one  of 
the  color-comparison  cylinders,  and  two  c.c.  each 
of  the  test  solutions  are  dropped  in.  It  is  con- 
venient to  have  a  pipet  for  each  solution,  and  to 
use  it  for  no  other  purpose. 

One  c.c.  of  the  standard  nitrite  solution  is 
placed  in  another  clean  cylinder,  made  up  with 
nitrite-free  water  to  25  c.c,  and  treated  with  the 
reagents  as  above. 

In  the  presence  of  nitrites  the  liquid  becomes 
pink.  At  the  end  of  five  minutes  the  two  solutions 
are  compared,  the  colors  equalized  by  diluting  the 
darker,  and  the  calculation  made  as  explained 
under  the  estimation  of  nitrates. 


SANITARY    EXAMINATIONS.  45 

The  reactions  consist  in  the  conversion  of  the 
sulfaniHc  acid  into  diazobenzenesulfonic  anhydrid, 
by  the  nitrite  present;  this  compound  is  then  in 
turn  converted  by  the  amidonaphthalene  into 
azo-a-amidonaphthalene-i-4-benzenesulfonic  acid. 
The  last-named  body  gives  the  color  to  the  liquid. 


OXYGEN-CONSUMING  POWER. 

All  organic  materials  being  more  or  less  easily 
oxidized,  several  methods  have  been  suggested  for 
determining  the  oxygen-consuming  powers  of 
waters  by  treatment  with  active  oxidizing  agents. 
These  methods  are,  however,  limited  in  value. 
The  organic  matters  in  water  differ  much  in 
character  and  condition,  and  their  oxidability  is 
subject  to  much  variation,  according  to  the  cir- 
cumstances under  which  the  test  is  made.  Never- 
theless, as  a  high  oxygen-consuming  power  cer- 
tainly indicates  departure  from  purity,  some  ad- 
ditional evidence  may  be  obtained.  Potassium 
permanganate  is  especially  suitable.  The  test  is 
usually  made  by  introducing  a  known  amount  of 
the  permanganate  into  the  water,  which  has  been 
rendered  acid,  and  measuring  after  a  definite 
period  the  proportion  which  has  been  decomposed. 

It  must  not  be  overlooked  that  if  a  water  con- 
tains nitrites,  ferrous  compounds,  or  sulfur  com- 
pounds  other   than   sulfates,    the   proportion   of 


46  ANALYTIC    OPERATIONS. 

oxygen  consumed  will  be  greater  than  that  re- 
quired for  the  organic  matter.  It  has  been  pro- 
posed, in  order  to  remove  the  nitrites  before  apply- 
ing the  permanganate,  to  take  500  c.c.  of  the 
water,  add  10  c.c.  of  the  dilute  sulfuric  acid,  boil 
for  twenty  minutes,  allow  to  cool,  and  then  treat 
with  permanganate.  Since,  however,  the  amount 
of  nitrites,  if  appreciable,  can  be  directly  deter- 
mined, it  is  more  satisfactory  to  deduct  from  the 
oxygen  consumed  the  amount  required  to  con- 
vert the  nitrites  present  into  nitrates,  and  the 
remainder  will  be  that  required  for  the  other 
oxidizable  ingredients.  Fourteen  parts  of  nitrogen 
existing  as  nitrite  require  16  parts  of  oxygen  for 
conversion  into  nitrate.  Similarly,  112  parts 
of  iron  in  a  ferrous  compound  will  require  16 
parts  of  oxygen  for  conversion  to  the  ferric  con- 
dition. 

Of  the  following  methods,  the  first,  due,  in  the 
main,  to  Tidy,  was  improved  by  Dupre,  and  ap- 
proved by  the  British  Society  of  Public  Analysts. 
Solutions  Required : 

Standard  Permanganate. — 0.395  gram  pure  po- 
tassium permanganate  dissolved  in  distilled  water, 
and  the  solution  made  up  to  1000  c.c.  One  c.c.  is 
equal  to  o.oooi  gram  oxygen. 

Diluted  Sulfuric  Acid. — Pure  sulfuric  acid  is 
diluted  with  twice  its  bulk  of  water,  and  then  a 
solution  of  potassium  permanganate  added  suffi- 


SANITARY    EXAMINATIONS.  47 

cient  to  give  a  faint  pink,  permanent  when  the 
liquid  is  heated  to  80°  F.  for  four  hours. 

Potassium  lodid. — Ten  grams  of  the  pure  sub- 
stance dissolved  in  100  c.c.  of  distilled  water. 

Sodium  Thiosulfate. — One  gram  of  the  pure 
crystallized  substance  dissolved  in  2000  c.c.  of  dis- 
tilled water. 

Starch  Indicator. — One  gram  of  clean  starch  is 
mixed  smoothly  with  cold  water  into  a  thin 
paste,  then  poured  gradually  into  about  200  c.c. 
of  boiling  water,  the  boiling  continued  for  one 
minute,  the  liquid  allowed  to  settle,  and  the  clear 
portion  used.  It  is  best  freshly  prepared. 
Analytic  Process : 

Two  determinations  are  made — one,  of  the 
oxygen  consumed  in  fifteen  minutes,  which  is  con- 
sidered to  represent  the  nitrites,  sulfids,  or  ferrous 
compounds,  and  the  other,  of  the  oxygen  con- 
sumed by  four  hours'  action.  Both  determina- 
tions are  made  at  a  temperature  of  80°  F.  Three 
glass-stoppered  bottles,  of  about  350  c.c.  capacity, 
are  rinsed  with  strong  sulfuric  acid  and  then  with 
water.  In  one  is  placed  250  c.c.  of  pure  distilled 
water  as  a  control  experiment,  and  in  each  of  the 
others  250  c.c.  of  the  water  to  be  tested.  The 
bottles  are  stoppered  and  brought  to  a  temperature 
of  80°  F. ;  10  c.c.  of  the  dilute  sulfuric  acid  and 
10  c.c.  of  the  standard  permanganate  are  added  to 
each,  and  the  stoppers  again  replaced.     At  the 


I 


48  ANALYTIC    OPERATIONS. 


I 


end  of  fifteen  minutes  one  sample  of  water  is 
removed  from  the  bath,  and  two  or  three  drops  of 
the  potassium  iodid  solution  added  to  remove  the 
pink.     After    thoro    admixture,    the    thiosulfate 
solution  is  run  in  from  a  buret  until  the  yellow  is 
nearly  destroyed,  a  few  drops  of  the  starch  solutiorij 
added,  and  the  addition  of  the  thiosulfate  con-' 
tinned  until  the  blue  is  quite  discharged.     If  the 
addition  of  the  thiosulfate  solution  has  been  prop4| 
erly  conducted,  one  drop   of   the   permanganat^ 
solution  will  restore  the  blue.  » 

The  other  bottles  are  maintained  at  80°  F.  for 
four  hours.  Should  the  pink  disappear  rapidly  in 
the  bottle  containing  the  water  under  examination, 
10  c.c.  of  the  permanganate  solution  must  be  added 
to  each  bottle,  in  order  to  maintain  a  distinct 
color.  At  the  end  of  four  hours  each  bottle  is 
removed  from  the  bath,  two  or  three  drops  of 
potassium  iodid  added,  and  the  titration  with 
thiosulfate  solution  conducted  as  just  described. 
The  calculation  is  most  conveniently  made  as 
follows : 

a  =  number   of  c.c.    required   for  the    control 

experiment. 
b  =  number  of  c.c.  required  for  the  water  under 

examination. 
c  =  available  oxygen  in  permanganate   (o.ooi 

for  10  c.c). 
X  —  oxygen  consumed  by  water. 
Then,  a  :  a-b  :  :c  :x. 


SANITARY    EXAMINATIONS.  49 

The  following  method  was  recommended  by  the 
Chemical  Section  of  the  American  Association  for 
the  Advancement  of  Science : 

''  Prepare  a  solution  of  potassium  permanganate 
containing  0.2  milligram  of  available  oxygen  to 
I  c.c.  and  a  solution  of  oxalic  acid  of  such  strength 
as  to  decompose  the  permanganate  solution, 
volume  for  volume,  the  strength  being  rede- 
termined from  time  to  time.  The  water  used  for 
making  these  solutions  should  be  purified  by 
distillation  from  alkaline  permanganate. 

''To  200  c.c.  of  water  to  be  examined,  in  a  400 
c.c.  flask,  add  10  c.c.  of  dilute  sulfuric  acid  (i  :  3) 
and  such  measured  quantity  of  the  permanganate 
as  will  give  a  persistent  color;  boil  ten  minutes, 
add,  if  necessary,  more  permanganate  in  measured 
quantities,  so  as  to  maintain  the  red  color;  re- 
move the  flask  from  the  lamp,  add  10  c.c.  of  oxalic 
acid  solution  to  destroy  the  color,  or  more  if 
required  by  the  excess  of  permanganate,  and 
then  add  permanganate,  drop  by  drop,  until  a 
faint  pink  appears.  From  the  total  quantity  of 
permanganate  used  deduct  the  equivalent  of  the 
oxalic  acid  used,  and  from  the  remainder  calculate 
the  milligrams  of  oxygen  consumed  by  the  ox- 
idizable  organic  matter  in  the  water/' 

The  oxygen-consuming  power  may  also  be 
indirectly  estimated  by  the  action  of  the  organic 
matter    upon    silver    compounds.      H.    Fleck's 


i 


50  ANALYTIC   OPERATIONS. 

method  depends  upon  the  reduction  produced  b 
boiling  the  water  with  alkaHne  solution  of  silve: 
thiosulfate  and  estimation  of  the  unreduced  silver. 
A.  R.  Leeds  has  proposed  a  method  by  treating  the 
water  with  decinormal  silver  nitrate,  exposing  to 
light  until  it  settles  perfectly  clear,  and  estimating 
the  reduced  silver. 

These  methods  are  open  to  practically  the  same 
objections  as  in  the  use  of  permanganate,  and  do 
not  seem  to  possess  any  decided  advantage. 
Qualitative  results  of  some  interest  may  occa- 
sionally be  obtained  by  the  following  method: 
Two  c.c.  of  a  one  per  cent,  solution  of  silver 
nitrate,  rendered  decidedly  alkaline  by  ammonium 
hydroxid,  are  added  to  100  c.c.  of  the  water  in  a 
stoppered  bottle,  which  is  then  placed  in  full  sun- 
light for  two  hours.  Waters  containing  but  little 
organic  matter  will  not  show  at  the  end  of  this 
period  any  appreciable  tint. 

PHOSPHATES. 
The  following  method  is  recommended  by  A.  G. 
Woodman : 
Solutions  Required : 

Ammonium  Molybdate  Solution. — 50  grams  in 
I  liter  of  distilled  water. 

Nitric  acid,  sp.  gr.  1.07. 

Sodium  Phosphate  Solution. — 0.5324  gram  crys- 
tallized disodium  hydrogen  phosphate,  100  c.c.  of 


SANITARY    EXAMINATIONS.  5 1 

the  above  nitric  acid,  distilled  water  sufficient  to 
make    looo    c.c.     This   is    equivalent   to    coooi 
phosphoric  anhydrid  in  i  c.c. 
Analytic  Process : 

Fifty  c.c.  of  the  sample  and  3  c.c.  of  nitric  acid 
are  evaporated  to  dryness  in  a  porcelain  dish  on 
the  water-bath,  the  residue  heated  for  two  hours 
at  100"^  C,  and  treated  with  50  c.c.  of  cold  distilled 
water  added  in  several  portions  which  are  mixed 
in  a  comparison  tube.  It  is  usually  unnecessary 
to  filter.  Four  c.c.  of  the  ammonium  molybdate 
solution  and  2  c.c.  of  nitric  acid  are  added,  the 
contents  mixed,  and  after  three  minutes  the  color 
compared  with  that  given  by  different  quantities 
of  the  standard  phosphate  solution  which  have 
been  made  up  to  50  c.c.  and  the  reagents  added  in 
the  same  amount  as  above. 

Blank  tests  must  be  made  to  determine  the 
purity  of  the  materials  used.  Distilled  water 
kept  for  some  time  in  glass  vessels  may  contain 
appreciable  amounts  of  substances  giving  color 
with  the  reagents. 

Ammonium  molybdate  solution  suitable  for  the 
gravimetric  determination  of  phosphates  may  be 
prepared  as  follows : 

Weigh  into  a  beaker  10  grams  of  pure  molyb- 
denum teroxid,  mix  well  with  40  c.c.  cold  distilled 
water,  and  add  8  c.c.  strong  ammonium  hydroxid, 


52  ANALYTIC    OPERATIONS. 

sp.  gr.  0.900.  When  completely  dissolved,  filter 
and  pour  slowly,  with  constant  stirring,  into  a 
mixture  of  40  c.c.  of  nitric  acid,  sp.  gr.  1.42,  and 
60  c.c.  of  water.  Add  0.005  gram  sodium  am- 
monium hydrogen  phosphate,  dissolved  in  a  little 
water,  agitate  well,  allow  precipitate  to  settle 
twenty-four  hours,  and  filter  before  using. 


DISSOLVED  OXYGEN. 

The  method  here  given,  a  modification  of  Mohr's, 
was  proposed  by  Blarez.     It  is  rapid  and  satis- 
factory. 
Solutions  Required : 

Sodium  Hydroxid. — Forty  grams  of  pure  sodium 
hydroxid  to  1000  c.c. 

Ferrous-ammonium  Sulfate, — Forty  grams  dis- 
solved in  about  1000  c.c.  of  water,  and  acidified 
with  a  few  drops  of  concentrated  sulfuric  acid. 

Decinormal  Potassium  Permanganate.  — 3 .156 
grams  in  1000  c.c.  of  distilled  water.  The  ac- 
curacy of  this  solution  should  be  determined  by 
titration  with  a  known  weight  of  ferrous-am- 
monium sulfate.  One  c.c.  should  be  equivalent 
to  0.0392  gram  ferrous  ammonium  sulfate  (0.0008 
gram  of  oxygen). 

The  apparatus  employed  (shown  in  Fig.  11)  is 
a  globular  separator,  of  about  250  .c.c.  capacity. 
Above  the  bulb  is  a  caoutchouc  stopper  carrying 


SANITARY    EXAMINATIONS. 


53 


a  cylindric  funnel,  of  about  12  c.c.  capacity, 
terminating  in  a  tube,  8  mm.  caliber,  sharply  con- 
tracted at  the  outlet  to  a  capillary  opening. 
The  tube  should  project  about  6  mm.  below  the 
stopper.  The  exact  capacity  of  the  apparatus  is 
measured  as  follows:  The  bulb  is  completely 
filled  with  water  and  the  stopper  inserted;  the 
level  of  the  water  will  rise  slightly  in  the  funnel 
tube,  and  should  be  brought  down  to  its  outlet  by 
drawing  a  little  off  at  the  stop-cock, 
after  which  the  water  is  run  into  a 
graduated  measure  and  its  volume 
noted. 
Analytic  Process : 

Thirty-five  c.c.  of  mercury  and  ten 
c.c.  of  sodium  hydroxid  solution  are 
put  into  the  bulb,  and  then  sufficient 
of  the  water  to  be  tested  to  fill  it. 
The  funnel  stopper  is  inserted,  and  the 
water  which  rises  into  the  funnel 
brought  into  the  bulb  by  cautiously 
running  out  at  the  stop-cock,  mer- 
cury, the  volume  of  which  should  be  noted. 
The  exact  volume  of  water  used  is  thus  known. 
Five  c.c.  of  the  ferrous  ammonium  sulfate  solution 
are  poured  into  the  funnel,  brought  into  the  bulb 
by  running  out  mercury,  and  the  liquid  thoroughly 
mixed  by  giving  the  apparatus  a  gyratory  move- 
ment.    After  standing  five  or  six    minutes  the 


Fig.  II. 


54  ANALYTIC    OPERATIONS. 

oxygen  will  be  completely  absorbed;  lo  c.c.  of 
the  diluted  sulfuric  acid  are  now  added  by  the 
same  method.  On  agitating  the  bulb,  the  con- 
tents become  clear.  The  watery  liquid  is  then 
transferred  to  a  beaker  and  titrated  with  deci- 
normal  permanganate.  A  volume  of  water  equal 
to  that  used  in  the  test  is  poured  into  another 
beaker,  lo  c.c.  each  of  the  sodium  hydroxid  and 
diluted  sulfuric  acid  added,  and  then  5  c.c.  of 
ferrous  ammonium  sulfate  solution.  The  result- 
ing liquid  is  titrated  with  permanganate.  The 
weight  of  oxygen  corresponding  to  the  difference 
between  the  two  titrations  gives  the  weight  of 
dissolved  oxygen  in  the  liquid  employed. 

Nitrates  do  not  appear  to  impair  the  accuracy  of 
this  method,  and  the  interfering  action  of  nitrites 
and  other  reducing  compounds  is  avoided  by  the 
control  experiment. 

It  is  perhaps  hardly  necessary  to  add  that  the 
exact  temperature  of  the  water  is  to  be  noted  at  the 
time  of  collection  of  the  sample. 

In  transferring  to  the  bulb,  the  water  should  be 
agitated  as  little  as  possible  in  contact  with  the 
air,  in  order  to  avoid  the  absorption  of  oxygen. 
A  siphon  should  be  used  for  this  purpose,  the 
lower  end  being  allowed  to  reach  to  the  bottom  of 
the  bulb. 


SANITARY    EXAMINATIONS.  55 

POISO/NOUS  METALS. 

Under  this  conventional  title  are  included 
barium,  chromium,  zinc,  arsenic,  copper,  and  lead. 
Manganese,  iron  and  aluminum  are  objectionable 
when  present  in  notable  amounts. 

Barium  is  rarely  present,  and  only  in  water 
containing  no  sulfates.  It  can  be  detected  and 
determined  by  slightly  acidifying  the  water  with 
hydrochloric  acid,  filtering  if  necessary,  and 
adding  solution  of  calcium  sulfate.  The  precipi- 
tated barium  sulfate  is  collected  and  weighed  in 
the  usual  way. 

Chromium  is  rarely  present,  but  may  be  looked 
for  in  the  waste  waters  of  dye-works  and  similar 
sources.  To  detect  it,  a  considerable  volume  of 
the  water  is  evaporated  to  dryness  with  addition  of 
a  small  amount  of  potassium  chlorate  and  nitrate, 
transferred  to  a  porcelain  crucible,  and  brought  to 
quiet  fusion ;  any  chromium  present  will  be  found 
in  the  residue  in  the  form  of  chromate.  The 
fused  mass,  after  cooling,  is  boiled  with  a  little 
water,  filtered,  the  filtrate  rendered  slightly  acid 
with  hydrochloric  acid,  and  a  solution  of  hydrogen 
dioxid  or  sodium  dioxid  added.  In  the  presence 
of  chromium  a  transient  blue  will  appear;  by 
adding  a  little  ether  and  shaking  the  mixture,  the 
color  will  pass  into  the  ether,  and  on  standing  a 
blue  layer  will  form  on  the  surface  of  the  water. 


56  ANALYTIC    OPERATIONS. 

Zinc  is  best  detected  by  the  test  described  by 
Allen.  The  water  is  rendered  slightly  alkaline  by 
addition  of  ammonium  hydroxid,  heated  to  boil- 
ing, filtered,  and  the  clear  liquid  treated  with  a 
few  drops  of  potassium  ferrocyanid;  in  the 
presence  even  of  the  merest  trace  of  zinc  a  white 
precipitate  will  be  produced. 

Arsenic  is  most  readily  detected  by  Reinsch's 
test.  A  considerable  volume  of  the  water  is 
rendered  slightly  alkaline  by  pure  sodium  car- 
bonate, and  evaporated  nearly  to  dryness  in  a 
porcelain  basin.  Two  or  three  c.c.  of  distilled 
water  strongly  acidulated  with  hydrochloric  acid 
are  placed  in  a  small  test-tube,  about  ^  of  a  square 
centimeter  of  bright  copper  foil  is  added,  and  the 
liquid  boiled  gently  for  a  few  minutes.  If  the 
copper  remains  bright,  showing  that  the  re- 
agents contain  no  arsenic,  the  water-residue  is 
acidified  with  hydrochloric  acid,  added  to  the 
contents  of  the  test-tube,  and  the  liquid  again 
boiled  for  several  minutes.  If  arsenic  is  present, 
a  steel-gray  stain  will  appear  on  the  copper.  The 
slip  is  removed,  washed  with  distilled  water, 
thoroly  dried  by  pressure  between  filter-paper, 
inserted  into  a  narrow  glass  tube  closed  at  one  end, 
which  has  been  previously  dried  by  heating  nearly 
to  redness.  The  tube  is  gently  heated  at  the 
point  at  which  the  copper  rests;  the  deposit  will 
sublime  and  collect  on  the  cooler  portion  of  the 


SANITARY    EXAMINATIONS.  57 

tube,  in  crystals  which  the  microscope  shows  to  be 
octahedral. 

Since  small  amounts  of  arsenic  frequently 
occur  in  reagents  and  in  glass  vessels,  care  must 
be  taken  to  avoid  such  sources  of  error.  Sodium 
carbonate  solution  may  contain  arsenic  dissolved 
from  the  glass  bottle  in  which  it  is  kept.  It  is 
best,  therefore,  to  use  the  solid  carbonate  for 
rendering  the  water  alkaline,  and  to  determine  its 
purity  before  use. 

For  very  delicate  testing  for  arsenic.  Marsh's 
test  should  be  used,  according  to  the  methods 
described  in  works  on  toxicology. 

Iron  is  detected  by  the  addition  of  a  drop  of 
ammonium  sulfid  to  the  water  in  a  tall  glass 
cylinder.  Ferrous  sulfid  is  formed  having  a 
greenish-black  color,  instantly  discharged  by 
acidifying  the  water  with  dilute  hydrochloric  acid. 
A  still  better  test  is  the  production  of  a  blood-red 
color,  with  potassium  thiocyanate,  due  to  the 
formation  of  ferric  thiocyanate.  The  water  should 
be  first  boiled  with  a  few  drops  of  nitric  acid,  to 
convert  the  iron  to  the  ferric  condition,  cooled,  and 
a  drop  or  two  of  the  solution  of  potassium  thio- 
cyanate added.  The  test  is  very  delicate.  Either 
of  the  above  tests  may  be  made  quantitative  by 
matching  the  color  produced  in  loo  c.c.  of  the 
water  with  that  obtained  from  a  known  weight  of 
iron.     The  method  with  potassium  thiocyanate 


58  ANALYTIC    OPERATIONS. 

is  preferable,  as  it  is  more  delicate  and  there  are 
fewer  interfering  conditions.     The  following  is  the 
method  as  elaborated  by  Thompson  and  described 
in  Sutton's  ''Volumetric  Analysis"  : 
Solutions  Required : 

Standard  Ferric  Sulfate. — 0.7  gram  ferrous  am- 
monium sulfate  is  dissolved  in  water  acidified  with 
sulfuric  acid,  and  potassium  permanganate  solu- 
tion added  until  the  solution  turns  a  very  faint 
pink  color.  The  solution  is  diluted  to  1000  c.c. 
One  c.c.  contains  o.oooi  gram  iron. 

Diluted  Nitric  Acid. — Thirty  c.c.  concentrated 
nitric  acid  diluted  with  water  to  about  100  c.c. 

Potassium  Thiocyanate.  — Five  grams  of  the  salt 
dissolved  in  about  100  c.c.  water. 
Analytic  Process : 

About  100  c.c.  of  the  water  are  evaporated  to 
small  bulk,  acidified  with  hydrochloric  acid,  and 
just  sufficient  dilute  potassium  permanganate 
solution  added  to  convert  all  the  iron  to  the  ferric 
condition.  The  liquid  is  evaporated  nearly  to 
dryness  to  drive  off  excess  of  acid,  then  diluted 
to  its  original  volume,  100  c.c.  In  two  tall  glasses 
marked  at  100  c.c,  5  c.c.  of  the  nitric  acid  and 
15  c.c.  of  the  thiocyanate  solution  are  placed.  To 
one  of  these  a  measured  volume  of  the  treated 
water  is  added  and  both  vessels  filled  up  to  the 
mark  with  distilled  water.  If  iron  is  present,  a 
blood-red  color  will  be  produced.     Standard  iron 


SANITARY    EXAMINATIONS.  59 

solution  is  added  to  the  second  vessel  until  the 
color  agrees.  The  amount  of  water  which  is 
added  to  the  first  glass  will  depend  upon  the 
quantity  of  iron  it  contains;  not  more  should  be 
used  than  will  require  two  or  three  c.c.  of  the 
standard  to  match  it,  otherwise  the  color  will  be 
too  deep  for  comparison. 

Manganese. — The  following  method  is  described 
by  Wanklyn  in  his  treatise  on  water  analysis. 
A  considerable  volume  (i.  e.,  1000  c.c.)  of  the  water 
is  evaporated  to  small  bulk,  nearly  neutralized 
by  hydrochloric  acid,  and  treated  with  a  few  drops 
of  a  solution  of  hydrogen  dioxid.  The  formation 
of  a  brown  precipitate  indicates  the  presence  of 
manganese.  The  test  is  very  delicate.  The  pre- 
cipitate may  be  collected  on  a  filter,  the  filter 
ashed,  and  the  residue  fused  with  a  mixture  of 
sodium  carbonate  and  potassium  nitrate.  Green 
potassium  manganate  will  be  produced,  which, 
when  boiled  with  water,  will  give  a  bright-red 
solution  of  potassium  permanganate.  The  quan- 
titative determination  is  given  elsewhere. 

Aluminum. — Traces  of  this  element  are  to  be 
expected  in  all  waters,  and  it  is  not  usual  to  test 
for  it  except  in  elaborate  analysis  of  the  mineral 
ingredients,  as  described  in  another  section.  The 
use  of  aluminum  sulfate  as  a  coagulant  in  many 
rapid-filtration  methods  makes  it  necessary  to 
examine  effluents  for  excess  of  precipitant,  and 


6o  ANALYTIC    OPERATIONS. 

this  may  be  done  by  the  following  method  devised 
by  Mrs.  Richards : 

To  25  c.c.  of  the  water  to  be  tested  (concentrated 
from  a  large  volume,  if  necessary)  is  added  a  few 
drops  of  freshly  prepared  logwood  decoction ;  any 
alkali  is  neutralized  and  the  color  is  brightened  by 
the  addition  of  two  or  three  drops  of  acetic  acid. 
By  comparison  with  standard  solutions,  the 
araount  of  alum  present  may  be  determined. 
One  part  of  alum  in  1,000,000  of  water  can  be 
detected  with  certainty.  In  cases  of  greater 
dilution,  concentration  of  larger  volumes  may  be 
necessary  to  obtain  a  decisive  test.  The  log- 
wood chips  yield  the  right  color  only  after  having 
been  treated  with  boiling  water  two  or  three 
times,  rejecting  the  successive  decoctions.  The 
first  portion  gives  a  yellow  color,  the  third  or 
fourth  usually  a  deep  red.  The  logwood  chips 
must  be  fresh. 

I  have  found  the  solution  of  sodium  alizarin- 
monosulfonate  (see  p.  15)  a  useful  reagent  for 
detecting  excess  of  aluminum  compounds  in 
water.  The  sample  should  be  filtered  and  a  few 
drops  of  the  indicator  solution  added.  When 
aluminum  compounds  are  present,  especially 
aluminum  sulfate,  the  reagent  assumes  a  yellow- 
ish color  and  becomes  much  less  sensitive,  so  that 
a  considerable  amount  of  decinormal  acid  can  be 
added  without  producing  the  acid  reaction.     If 


SANITARY    EXAMINATIONS.  6l 

another  equal  portion  of  the  sample  is  treated  with 
a  small  amount  of  sodium  carbonate,  allowed  to 
stand  an  hour  or  so,  filtered  and  tested  with  the 
indicator,  the  difference  in  reaction  will  be  marked 
if  the  sodium  carbonate  has  been  added  in  quan- 
tity sufficient  to  overcome  the  aluminum  com- 
pound present. 

Lead  may  be  readily  detected  by  adding  to  the 
water  in  a  tall  glass  cylinder  a  drop  of  ammonium 
sulfid;  brownish-black  lead  sulfid  is  formed, 
which  does  not  dissolve  either  by  acidulating  the 
water  with  dilute  hydrochloric  acid  (distinction 
from  iron),  nor  by  the  addition  of  about  one  c.c. 
of  a  strong  solution  of  potassium  cyanid  (dis- 
tinction from  copper).  S.  Harvey  gives  the 
following  method:  250  c.c.  are  placed  in  a  pre- 
cipitating jar,  about  o.i  gram  of  crystallized 
potassium  dichromate  is  added  and  dissolved  by 
agitation.  The  same  volume  of  lead-free  water 
is  treated  in  the  same  manner,  and  the  two  solu- 
tions placed  side  by  side.  Water  containing  0.3 
part  per  million  will  show  a  turbidity  in  fifteen 
minutes  which  will  be  rendered  more  distinct  by 
contrast  with  the  clear  water  alongside.  By 
allowing  the  jar  to  stand  for  about  twelve  hours 
undisturbed,  the  precipitate  will  settle  and  will 
become  still  more  distinct.  No  other  metal 
likely  to  be  present  in  water  will  give  a  similar 
reaction. 


62  ANALYTIC    OPERATIONS. 

In  the  absence  of  copper  the  amount  of  lead 
present  may  be  determined  as  follows :  A  solution 
is  prepared  containing  1.6  grams  of  lead  nitrate 
to  1000  c.c. ;  one  c.c.  of  this  contains  one  milligram 
lead.  One  hundred  c.c.  of  the  water  to  be  tested 
are  placed  in  a  tall  glass  vessel,  made  acid  by  the 
addition  of  a  few  drops  of  acetic  acid,  and  five  c.c. 
of  hydrogen  sulfid  added.  In  a  similar  vessel 
100  c.c.  of  distilled  water  are  placed,  together 
with  the  same  quantities  of  acetic  acid  and  hy- 
drogen sulfid,  and  sufficient  of  the  standard  lead 
solution  to  match  the  tint  in  the  first  cylinder. 
The  amount  of  lead  in  the  water  under  examina- 
tion is  thus  known. 

Copper.  As  copper  sulfate  is  now  used  for 
preventing  vegetable  growths  in  water,  it  is  often 
necessary  to  test  for  it.  When  present  in  appre- 
ciable amount,  it  may  be  detected  by  acidifying 
with  acetic  acid  and  adding  hydrogen  sulfid.  The 
precipitate  is  distinguished  from  lead  sulfid  by 
the  fact  that  the  color  is  discharged  on  the  ad- 
dition of  about  I  c.c.  of  a  strong  solution  of  pure 
potassium  cyanid.  The  presence  of  copper  may 
be  confirmed  by  the  addition  of  a  solution  of 
potassium  ferrocyanid  to  another  portion  of  the 
water.  In  the  presence  of  even  a  very  small 
amount  of  copper,  a  mahogany-red  color  is  pro- 
duced. 

H.  C.  Bradley  has  found  that  logwood  hema- 


I 


SANITARY    EXAMINATIONS.  63 


toxylon  is  a  delicate  test  for  copper.  It  is  best 
used  in  weak  alcoholic  solution  to  which  a  trace  of 
sodium  hydroxid  has  been  added  so  as  to  render 
it  faintly  pink.  A  few  drops  of  this  reagent  added 
to  a  moderate  volume  of  the  sample  will  in  the 
course  of  a  few  minutes  develop  a  distinct  blue, 
even  if  very  small  amounts  of  copper  are  present. 
Larger  amounts  of  copper  produce  a  deep  blue 
precipitate.  The  liquid  should  be  allowed  to 
stand  for  an  hour  or  so  before  deciding  that  the 
test  is  negative.  Bradley  has  found  that  free 
mineral  acid  interferes  with  the  test. 

In  the  absence  of  lead,  copper  is  determined  in 
the  same  way  as  that  metal,  using,  however,  a 
standard  solution  of  copper  for  the  comparison 
liquid.  This  is  made  by  dissolving  3.929  grams  of 
crystallized  copper  sulfate  in  one  liter  of  water. 
One  c.c.  of  the  solution  contains  one  milligram 
copper. 

If  both  lead  and  copper  are  present,  a  large 
quantity  of  the  water  should  be  evaporated  to 
small  bulk,  and  the  metals  separated  and  deter- 
mined by  any  one  of  the  ordinary  laboratory 
methods. 


BIOLOGIC  EXAMINATIONS. 

In  a  comprehensive  sense  the  living  organisms 
of  water  include  representatives  of  all  the  great 


64  ANALYTIC    OPERATIONS. 

groups  of  animals  and  plants.  The  higher  orders 
of  organic  forms  are  absent  from  very  foul  water. 
From  an  analytic  point  of  view,  observation 
is  limited  to  the  determinations  of  those  forms 
which  are  inappreciable  to  the  unassisted  eye. 
So  far  as  regards  some  of  the  moderately  com- 
plex organisms,  such  as  the  minute  crustaceans, 
algae,  diatoms,  and  even  ameb^,  it  may  be  said 
that  while  some  general  inferences  as  to  the 
character  and  history  of  the  water  may  be  de- 
duced from  an  identification  of  the  specific  forms, 
no  sanitary  signification  can  be  attached  to  them, 
except  that  they  are  objectionable.  From  what 
is  now  known  of  the  life-history  of  parasitic 
organisms,  it  is  evident  that  water  that  is  freely 
accessible  to  animal  forms  is  liable  to  be  danger- 
ously polluted.  Moreover,  the  dead  bodies  of 
such  animals  will  furnish  food  to  many  forms  of 
microbes  and  thus  assist  in  the  multiplication  of 
the  latter.  The  ova  of  the  entozoa  might  in  some 
cases  be  detected  by  careful  search,  and  would 
indicate  recent  pollution  of  a  highly  dangerous 
character. 

The  number  of  the  higher  forms  present  in  any 
sample  will  depend  very  much  upon  the  point  at 
which  it  is  collected,  they  being  more  numerous 
in  the  neighborhood  of  abundant  vegetable 
growths,  and  at  the  bottom  and  sides  of  streams. 

Several  observers,  notably  Sedgwick  and  Rafter, 


SANITARY    EXAMINATIONS.  65 

have  paid  considerable  attention  to  the  recog- 
nition of  the  animal  and  vegetable  forms  in  surface 
waters.  Some  of  these  forms  cause  disagreeable 
odors  and  colors ;  in  the  warm  season  of  the  year, 
when  such  water  is  stored  in  reservoirs,  consider- 
able annoyance  is  felt  by  the  users,  and  the  en- 
gineer-in-charge  is  subjected  to  much  criticism. 
It  has  been  found  that  even  crude  filtration 
methods,  such  as  allowing  the  water  to  pass  thru 
a  dike  of  porous  soil  before  storing  it  in  a  reservoir, 
will  diminish  the  tendency  to  these  conditions. 
Cleansing  a  reservoir — disinfecting  the  inner 
surface,  for  instance,  by  whitewashing — has  also 
improved  the  condition. 

Observation,  especially  in  Massachusetts,  has 
shown  that  reservoirs,  intended  for  even  moder- 
ately prolonged  storage  of  water,  should  be  clean — 
that  is,  organic  matter  of  any  kind  should  not  be 
allowed  to  accumulate  on  the  bottom  and  sides. 
Drown  states  that  while  the  water  in  one  basin 
became  foul  from  stagnation,  in  another  which 
was  carefully  prepared  by  the  removal  of  all  soil 
and  vegetable  matter,  and  is  supplied  by  a  brown, 
swampy  water  from  a  district  almost  entirely 
free  from  pollution,  the  water  is  good  at  a  depth  of 
forty  feet. 

In  Philadelphia,  where  large  storage  reservoirs 
are  used  for  water  that  is  often  very  muddy,  but 
little  trouble  from  the  growth  of  microscopic 
5 


66  ANALYTIC    OPERATIONS. 

organisms  occurs.  These  reservoirs  are  artificial 
basins. 

Sedgwick's  method  of  collecting  organisms 
other  than  microbes,  with  some  modifications  by 
Williston,  is  as  follows : 

In  ordinary  cases  about  loo  c.c.  are  employed. 
Sometimes  it  will  be  advantageous  to  use  double 
this  quantity,  at  other  times  much  less.  In  rare 
cases  the  examination  can  be  made  upon  unfiltered 
water.  Originally  sand  was  employed  for  a 
filter  material,  but  Williston  finds  that  precipitated 
silica,  made  by  decomposing  silicon  fiuorid  with 
water,  is  more  satisfactory.  This  precipitated 
silica  is  a  commercial  article,  and  its  method  of 
preparation  is  given  in  all  the  larger  manuals  of 
chemistry. 

A  small  glass  funnel  with  an  even-calibered 
stem  is  selected,  and  the  lower  end  of  the  stem 
plugged  with  a  little  absorbent  cotton,  upon  which 
a  layer  three  or  four  mm.  deep  of  the  filter-mate- 
rial is  placed.  The  requisite  volume  of  water  is 
then  allowed  to  filter  thru.  The  pledget  of  cotton 
is  removed,  and  the  filter-material  is  washed  down 
with  filtered  or  distilled  water  into  a  cell  intended 
for  microscopic  examination.  This  cell  is  a  glass 
plate  accurately  ruled,  to  which  is  attached  a 
brass  cell  50  mm.  long  by  10  mm.  wide,  of  depth 
sufficient  to  hold  about  two  c.c.  of  water.  After 
the  material  has  been  allowed  to  distribute  itself 


SANITARY    EXAMINATIONS. 


67 


and  settle  in  the  cell,  it  is  examined  with  a  moder- 
ate power,  and  the  different  organisms  in  a  vary- 
ing number  of  the  squares  counted.  Each  or- 
ganism may  be  counted  by  itself,  if  occurring  in 
large  numbers,  the  average  of  a  few  squares  being 
sufficient  for  the  purpose.     Organisms  less  numer- 


B 


Sedgwick'-Rifter 
B1587. 


ously  represented  may  be  counted  by  averaging  a 
larger  number  of  squares.  Figure  12  (loaned  by 
the  Arthur  H.  Thomas  Co.)  shows  a  more  elab- 
orate form  of  this  filter. 

Filtering  in  this  manner  can  not  be  relied  upon 
in  all  cases.  Indeed,  in  most  cases  the  unfiltered 
water  also   should  be  examined.     Some  of  the 


68  ANALYTIC    OPERATIONS. 

minute  unicellular  organisms  pass  thru  a  small 
extent  of  sand  or  precipitated  silica,  or  even 
filter-paper. 

It  is  not  unlikely  that  the  high-speed  centrif- 
ugal apparatus  now  used  in  laboratories,  associ- 
ated with  the  employment  of  some  fine  precipitant, 
will  aid  in  these  investigations. 

Dibdin  prepares  as  follows,  a  ''micro-filter," 
for  the  collection  of  minute  suspended  matters: 
A  piece  of  combustion-tubing  20  to  25  cm.  long  is 
cleaned  and  drawn  out  in  the  middle  to  a  capillary 
tube,  and  broken  by  a  file  scratch  at  a  point  at 
which  the  caliber  is  not  more  than  two  milli- 
meters. Each  of  these  pieces  serves  for  a  filter. 
A  mixture  of  equal  parts  of  air-dried  clay  and 
infusorial  earth  is  made  into  a  smooth,  stiff  paste 
with  water  and  spread  out  on  a  slab  in  a  layer 
about  two  millimeters  deep.  The  capillary  end  of 
a  tube  is  pressed  down  into  the  mass  and  moved  in 
a  circle  until  a  plug  is  formed.  This  is  warmed 
until  dry,  and  heated  to  redness,  forming  a  close 
filter. 

The  water  to  be  examined  is  filtered  in  con- 
siderable amount, — 1000  c.c,  for  example,  if 
there  is  but  little  suspended  matter, — first  thru 
a  hardened  paper  filter  placed  in  a  funnel,  pre- 
cautions being  taken  to  exclude  dust.  The 
deposit  is  washed  from  the  filter-paper  into  the 
micro-filter  by  means  of  a  jet  of  pure  water.     The 


SANITARY    EXAMINATIONS.  69 

suspended  matter  collects  on  the  top  of  the  clay 
plug  and  is  measured  by  noting  its  height.  If  the 
clay  plug  is  blocked,  the  application  of  a  filter- 
pump  may  be  needed.  When  the  column  of 
water  in  the  small  tube  is  only  about  a  centi- 
meter in  height,  the  main  body  of  the  tube  is  cut 
away  by  means  of  a  file  scratch  and  the  deposit 
loosened  from  the  filter  plug,  if  necessary,  by  the 
use  of  a  platinum  wire.  The  tube  is  inverted  so 
as  to  bring  the  deposit  to  the  open  end,  and  then 
cut  off  close  to  the  plug.  By  this  means  the  sus- 
pended matter  is  collected  in  a  short  capillary 
tube  open  at  both  ends.  By  gentle  shaking,  the 
contents  may  be  brought  onto  a  glass  slide. 

Owing  to  the  great  differences  in  the  size  of 
microscopic  organisms,  the  mere  enumeration  of 
their  numbers  is  not  always  an  index  of  the 
araount  of  living  matter  in  suspension.  To 
obviate  this,  Whipple  has  suggested  a  standard 
unit  of  size,  estimating  by  means  of  it  the  total 
volume  of  the  organisms,  and  not  their  number. 
He  finds  by  this  method  that  the  analytic  and 
biologic  results  correspond  much  more  closely 
than  when  mere  numbers  are  recorded.  The 
unit  is  an  area  of  400  microns — that  is,  a  square  of 
20  microns  on  a  side.  The  results  are  stated  in 
number  of  standard  units  per  cubic  centimeter. 

Whipple  has  investigated  the  conditions  in- 
fluencing the  growth  of  the  microscopic  organisms 


70  ANALYTIC    OPERATIONS. 

in  water.  He  finds  that  diatoms  thrive  best  with 
a  supply  of  nitrates  and  a  free  circulation  of  air; 
temperature  alone  has  no  very  direct  effect. 
Infusoria  will  be  found  in  largest  numbers  when 
the  water  contains  the  greatest  amount  of  finely 
divided  organic  matter.  When  the  conditions 
bring  about  a  circulation  of  the  water,  the  or- 
ganisms are  not  only  brought  constantly  in  con- 
tact with  new  food  materials,  but  are  enabled  to 
reach  the  upper  layers  of  the  water  where  oxygen 
is  abundant. 

Bacteriologic  examinations  may  be  qualitative  or 
quantitative.  The  former  involves  the  determina- 
tion of  the  species  of  microbes  present,  especially 
those  having  disease-producing  power,  or  charac- 
teristic of  some  form  of  pollution.  The  processes 
are  usually  laborious,  requiring  extensive  lab- 
oratory facilities.  Quantitative  examination — 
microbe-counting,  as  it  may  be  called — is  the  deter- 
mination of  the  number  of  microbes,  or  microbe- 
colonies,  that  can  be  grown  from  a  given  volume  of 
water  under  specified  conditions.  As  the  growth 
of  living  organisms  is  influenced  by  all  external 
conditions,  the  results  of  the  culture  of  microbes 
are  not  comparable  with  one  another,  unless  strict 
uniformity  of  methods  has  been  observed.  Neg- 
lect of  this  fact  renders  a  very  large  part  of  the 
earlier  work  and  some  of  the  present-day  work 
of  little  statistical  value.     Among  the  conditions 


SANITARY    EXAMINATIONS.  7 1 

materially  affecting  the  growth  of  microbes  are 
temperature,  reaction  of  the  culture-medium  to 
different  indicators,  degree  of  exposure  to  light  and 
air,  and  duration  of  cultivation.  The  composition 
of  the  culture -medium  has  much  influence,  and  it 
is  difficult  to  control  this  exactly,  owing  to  the 
irregularity  of  quality  of  some  of  the  materials 
used. 

At  the  present  day  microbe-counting  for  water 
analysis  is  done  almost  entirely  with  culture- 
media  that  are  solid  at  ordinary  temperatures,  but 
may  be  liquefied  at  or  near  blood-heat.  Gelatin 
or  agar  is  used  for  producing  the  solidity.  The 
former  is  the  most  convenient,  but  its  jelly  melts 
at  such  a  low  temperature  that  it  is  of  limited  ap- 
plication, and  agar  is  largely  employed. 

Apparatus  for  bacteriologic  work  is  now  all 
furnished  of  good  quality  by  dealers,  and  will  not 
need  special  description.  For  the  ordinary  meth- 
ods of  microbe-counting  the  following  will  be 
needed : 

Open-steam  Sterilizer.  A  modification  of  the 
Arnold  sterilizer  j.s  now  much  used. 

Autoclave,  a  closed-steam  sterilizer,  permitting 
the  application  of  temperatures  much  above  the 
boiling  point  of  water. 

Hot-air  Oven  for  special  sterilizations. 

Culture  Oven,  with  thermostat. 

Double  Boiler  of  agate  or  other  good  culinary 


72  ANALYTIC    OPERATIONS. 

ware.  The  inner  vessel  should  have  a  capacity  of 
a  little  more  than  looo  c.c. 

Test-tubes,  about  12  cm.  long  and  1.5  cm.  in 
diameter. 

Petri  dishes,  about  10  cm.  in  diameter  and  i.o 
cm.  deep.  As  far  as  possible,  dishes  of  uniform 
size  should  be  selected.  Each  dish  and  cover 
should  be  marked  in  the  center  by  a  diamond  with 
a  distinguishing  number. 

Wire  baskets  for  holding  several  dozen  test- 
tubes. 

Fermentation-tubes,  such  as  used  in  the  detection 
of  sugar  in  urine. 

Ordinary  laboratory  appliances,  such  as  pipets, 
burets,  funnels,  beakers,  and  cotton-wool.  Tin- 
foil cut  in  squares  5  cm.  on  the  side. 

Sterilization  in  the  autoclave  is  much  in  favor 
in  laboratories  in  which  much  work  is  done,  as  it  is 
efficient  and  rapid,  but  the  high  temperature  has 
a  greater  chemical  action  upon  some  of  the  media 
than  that  of  the  open  steam  sterilizer.  Sufficient 
sterilization  for  work  in  water  analysis  can  be 
accomplished  by  the  latter  method,  especially  if 
several  short  treatments,  say  of  a  half  hour  each, 
at  intervals  of  twenty-four  hours,  are  employed. 

The  materials  for  preparing  culture-media  should 
be  obtained  from  responsible  dealers,  who  will 
furnish  the  grades  regularly  used.  The  follow- 
ing will  assist  in  the  selection. 


SANITARY    EXAMINATIONS.  73 

Gelatin,  A  grade  made  in  Germany  and  dis- 
tinguished by  a  monogram  of  the  initials  WH  is 
used. 

Agar.     A  colorless  grade  is  preferable. 

Peptone.     Witte's  dry  peptone  is  used. 

Dextrose.  The  grade  termed ' '  crystallized  pure ' ' 
(often  called  '*  glucose")  is  preferred. 

Meat-extract.  That  made  by  the  Liebig  Meat- 
Extract  Company,  limited,  of  London,  is  largely 
used  by  bacteriologists,  but  there  seems  to  be  no 
reason  for  preferring  it  to  the  best  American 
extracts. 

Sodium  chlorid.  A  good  quality  of  table  salt 
will  suffice. 

Glycerol  should  be  as  free  as  possible  from  acid 
and  mineral  matters. 

Lactose  should  be  of  high  purity,  especially  free 
from  milk-proteids. 

I  have  found  samples  of  the  imported  (WH) 
gelatin  so  largely  used  by  American  bacteriolo- 
gists, showing  a  reaction  with  iodin  like  that  given 
by  sulfites.  As  sulfurous  acid  may  be  used  for 
bleaching,  some  of  this  might  remain  in  the 
finished  product.  It  would  be,  of  course,  very 
objectionable  in  culture-media.  To  avoid  this 
impurity,  each  lot  of  gelatin  should  be  tested  by 
allowing  a  weighed  amount  (say  lo  grams)  to  soak 
overnight  in  cold  water,  then  completing  the 
solution  by  gentle  warming,  allowing  the  liquid 


74  ANALYTIC    OPERATIONS. 

to  cool,  and  titrating  with  centinormal  iodin  in 
presence  of  sulfuric  acid  and  starch  solution,  as  in 
the  usual  process  for  estimation  of  total  sulfites 
in  food  products.  A  sample  of  gelatin  so  tested 
should  require  less  than  2  c.c.  of  the  iodin  solution. 
It  is  not  unlikely  that  the  preference  for  imported 
gelatin  involves  a  useless  expense  to  bacteriolo- 
gists. I  have  found  a  sample  of  American  manu- 
facture known  as  '' Marblehead"  to  show  a  very 
slight  reaction  with  iodin. 
Preparation  of  Culture-media : 

Bouillon  is  the  term  applied  to  many  forms  of 
liquid  media,  prepared  with  meat-juice  or  meat- 
extract.  The  ordinary  bouillon  is  prepared  ac- 
cording to  the  following  formula : 

Five  hundred  grams  of  finely  chopped  meat, 
as  free  as  possible  from  fat  and  gristle,  are  soaked 
overnight  in  about  a  liter  of  cold  water,  at  a 
temperature  between  0°  C.  and  10^  C.  The  mass 
is  then  strained  thru  a  coarse  towel  and  pressed 
until  as  much  as  possible  of  the  liquid  is  obtained. 
To  this  is  added  10  grams  of  peptone  and  5  grams 
of  common  salt.  It  is  then  heated  to  boiling,  best 
in  the  open-steam  sterilizer,  to  coagulate  albumin, 
after  which  it  is  filtered.  The  most  difficult  point 
in  the  work  is  neutralization.  This  is  often  ac- 
complished by  the  use  of  sodium  carbonate,  which 
is  added  in  small  amounts  until  the  liquid  no 
longer    affects    red    litmus    paper.     The    better 


I 


SANITARY    EXAMINATIONS.  75 


method  is  to  titrate  a  portion  of  the  bouillon  with 
sodium  hydroxid  solution,  and  calculate  from  this 
the  amount  of  that  solution  necessary  to  neutral- 
ize the  whole  of  the  liquid.  Fuller  has  devised  a 
good  method  of  procedure.  The  bouillon  is  made 
up  when  cool  to  a  definite  volume,  say  looo  c.c. ; 
5  c.c.  are  mixed  with  45  c.c.  of  distilled  water  in  a 
porcelain  dish,  boiled  for  three  minutes,  i  c.c.  of 
solution  of  phenolphthalein  added,  and  quickly 
titrated  with  twentieth  normal  sodium  hydroxid. 
The  neutral  point  is  the  slight  pink  color  not  dis- 
appearing on  gentle  stirring.  From  the  number 
of  cubic  centimeters  used  the  amount  of  alkali 
needed  to  neutralize  the  whole  solution  is  cal- 
culated, but  this  alkali  should  be  added  in  the 
form  of  normal  solution  in  order  to  avoid  much 
dilution  of  the  bouillon. 

Meat-extract  is  often  used  instead  of  the  in- 
fusion of  chopped  meat.  Five  grams  of  a  good 
commercial  extract  are  used  for  each  1000  c.c.  of 
bouillon. 

Bouillon  may  be  modified  in  many  ways,  by  the 
addition  of  different  substances,  but  the  inherent 
or  possible  acidity  or  alkalinity  of  these  must  be 
ascertained  and  corrected  if  culture  results  are  to 
be  kept  standard. 

Dextrose  Bouillon.  For  special  -fermentation 
work  a  solution  is  made  by  adding  dextrose  in  the 
proportion  of  20  grams  to  1000  c.c.  of  the  liquid. 


76  ANALYTIC    OPERATIONS. 

Gelatin  Media. — The  ingredients,  other  than  the 
gelatin,  are  dissolved  and  treated  as  described  in 
the  making  of  bouillon.  After  neutralization,  the 
gelatin  is  dissolved  by  gentle  heating.  If  this 
contributes  any  acidity,  it  must  be  neutralized. 
The  liquid  should  not  be  heated  strongly  or  for  a 
long  time,  as  the  gelatinizing  property  may  be 
injured.  The  solution  is  made  up  to  the  proper 
volume  and  filtered  thru  paper. 

Meat-extract  peptone-gelatin: 

Meat-extract, 5.0  grams 

Peptone, lo.o        '' 

Gelatin, 1 50.0        '' 

Dextrose, 2.0        '' 

Sodium  chlorid, 5.0        " 

Water, 1 000.0  c.c. 

Agar  Media: 

The  preparation  of  agar  solution  is  more  diffi- 
cult than  that  of  gelatin.  Several  methods  have 
been  suggested.     Ravenel  uses  the  following : 

Preferable  Method: 

(A)  Chopped  meat, 500  grams 

Water, 500  c.c. 

These  are  mixed  and  allowed  to  stand  over- 
night. 

(B)  Agar,.". 12  grams 

Water, 500  c.c. 


SANITARY    EXAMINATIONS.  77 

Solution  B  is  put  into  the  autoclave,  the  pres- 
sure run  up  to  2  atmospheres,  the  heat  withdrawn, 
and  the  boiler  opened  when  the  temperature  has 
fallen  a  little  below  ioo°  C.  The  solution  is 
allowed  to  cool  to  about  75°  C.  (below  the  co- 
agulating point  of  albumin)  10  grams  of  dried 
peptone  and  5  grams  of  sodium  chlorid  are  added, 
A  and  B  mixed,  the  liquid  boiled  for  about  three 
minutes,  neutralized  and  filtered.  The  filtration 
is  very  quick — from  ten  to  twelve  minutes  for 
1000  c.c.  A  hot-water  funnel  is  not  needed,  but 
the  filter  must  be  moistened  with  boiling  water 
immediately  before  pouring  in  the  agar.  In  the 
process  with  fresh  meat  the  clarification  is  effected 
by  the  coagulation  of  the  albumin  in  the  meat- 
water,  hence  solution  B  must  not  be  added  to  A 
until  cool  enough  to  avoid  coagulation. 

Alternative  method: 

(A)  Dried  peptone, .  .  .- 10  grams 

Common  salt, S       '' 

Meat-extract, 5       ** 

Water, 500  c.c. 

Boil  for  three  minutes  and  neutralize. 

(B)  Agar-agar, 12  grams 

Water, 500  c.c. 

The  agar  is  chopped  fine  and  heated  in  the  auto- 
clave to  two  atmospheres.  As  soon  as  this  pres- 
sure is  reached,  the  heat  is  withdrawn  and  the 


78  ANALYTIC    OPERATIONS. 

liquid  allowed  to  cool  until  below  ioo°  C.  before 
opening.  The  two  solutions  A  and  B  are  then 
mixed,  cooled  to  60^  C,  the  whites  of  two  eggs 
beaten  in  50  c.c.  of  water  added,  well  stirred  in, 
and  the  whole  then  boiled  and  filtered  thru  paper. 

Instead  of  the  white  of  egg,  blood-serum  may 
be  used,  which  seems  to  add  also  to  the  nutritive 
value  of  the  medium.  Agar  made  with  meat- 
extract  will  often  form  a  precipitate  during  the 
sterilization. 

Abbott  gives  the  following  method  of  preparing 
agar  solution:  The  bouillon  is  prepared  and 
neutralized  in  the  usual  way,  then  15  grams  of 
finely  chopped  agar  are  added,  and  water  suffi- 
cient to  make  the  volume  1250  c.c.  The  mass  is 
boiled  gently  over  a  direct  flame,  stirring  occa- 
sionally for  several  hours.  If  the  fluid  goes  below 
the  liter  level,  enough  water  should  be  added  to 
make  up  the  amount.  The  boiling  should  be  con- 
tinued until  about  1000  c.c.  is  left  in  the  vessel. 
When  the  solution  of  the  agar  is  attained,  the: 
vessel  is  placed  in  a  large  dish  of  cold  water  untill 
it  has  cooled  to  about  70°  C,  the  white  of  one  egg 
that  has  been  beaten  up  with  water  added,  mixedl 
well,  and  boiled  again  for  a  half -hour,  avoiding' 
the  evaporation  of  the  liquid  below  1000  c.c. 
The  liquid  is  filtered  thru  heavy  folded  filter-paper 
at  room-temperature.  It  is  necessary  that  the 
solution  should  be  not  above  70°  C.  when  the 


SANITARY    EXAMINATIONS.  79 

white  of  egg  is  added  or  it  will  become  lumpy. 
Commercial  egg-albumin  in  lo  per  cent,  solution 
in  water  may  be  used  instead  of  white  of  egg. 
The  solution  thus  prepared  should  filter  rapidly. 

Potato  Culture, — Cultivation  on  potatoes  has 
been  much  used  as  a  method  of  distinguishing 
certain  microbes.  Large,  sound  potatoes  should 
be  selected,  thoroly  washed,  and  cut  into  disks 
about  five  centimeters  in  diameter  and  one  cen- 
timeter thick.  These  are  placed  in  glass  boxes 
(pomade  boxes)  which  have  lids  with  ground 
joint,  and  heated  for  about  one-half  hour  in  the 
sterilizer.  Another  method  is  to  cut  out  cylinders 
with  the  aid  of  an  apple -corer,  or  largest  size 
cork-borer,  slice  these  obliquely,  and  place  them  in 
test-tubes,  which  are  then  closed  with  cotton 
plugs  and  sterilized.  The  latter  method  does  not 
give  a  large  surface,  but  the  growth  of  any  in- 
oculation may  be  easily  watched: 

Milk  Culture.  Milk,  deprived  of  most  of  its 
fat,  is  used  for  the  purpose  of  detecting  microbes 
that  produce  notable  amounts  of  acid.  The  fol- 
lowing is  the  procedure  generally  recommended: 
Milk  as  pure  as  can  be  obtained  is  allowed  to 
stand  over  night  in  a  refrigerator,  the  cream 
removed,  and  the  skimmed  milk  siphoned  off  from 
any  sediment.  It  should  show  not  more  that  i% 
of  acidity  to  normal  alkali  (that  is,  loo  c.c.  of  the 
milk  should  not  require  more  than  i  c.c.  of  normal 


8o  ANALYTIC    OPERATIONS. 

sodium  hydroxid  to  neutralize,  using  phenol- 
phthalein  as  an  indicator) .  Whqn  the  proper  con- 
dition in  this  respect  has  been  obtained,  the  milk 
may  be  sterilized  in  tubes  as  usual.  Azolitmin  solu- 
tion in  small  amount  may  also  be  added  if  desired. 

The  tubes  containing  the  sterilized  milk  are 
inoculated  with  small  amounts  of  the  sample,  to 
be  tested,  kept  for  twenty-four  hours  or  even 
longer,  at  blood  heat,  and  then  tested  by  heating 
to  the  boiling-point.  If  coagulation  occurs,  acid- 
producing  microbes  are  present. 

Many  special  forms  of  culture-media  are  em- 
ployed for  bacteriologic  investigations  which  do 
not  come  within  the  line  of  water  analysis,  and 
need  not  be  described.  One  form  is  much  em- 
ployed in  the  search  for  the  specific  germ  of  ty- 
phoid fever,  namely,  Wurtz's  litmus-lactose  me- 
dium. This  may  be  with  either  agar  or  gelatin, 
in  conjunction  with  meat-extract.  The  nutrient 
medium  must  be  made  so  as'  to  possess  such  a 
degree  of  alkalinity  that  lo  c.c.  will  neutralize  0.5 
c.c.  of  decinormal  sulfuric  acid.  Lactose  is  added 
in  the  proportion  of  two  or  three  grams  to  100  c.c. 
of  medium  and  the  mixture  sterilized,  after  which 
sufficient  sterilized  azolitmin  solution  is  added  to 
give  the  fluid  a  distinct  but  not  deep-blue  tint. 

Cultivation  in  gelatin  at  ordinary  temperatures 
usually  yields  a  larger  number  of  points  of  mi- 
crobic  life  than  in  agar  at  blood-heat.     This  is 


SANITARY    EXAMINATIONS.  8l 

due  to  the  fact  that  many  common  water-bacteria 
do  not  grow  well  at  the  higher  temperatures. 

Culture-media  when  ready  for  use  are  distri- 
buted in  test-tubes.  These  must  be  well  cleaned. 
In  laboratories  in  which  regular  chemical  work  is 
done,  the  solution  of  crude  chromic  and  sulfuric 
acids  used  for  voltaic  batteries  is  a  good  cleaning 
agent,  the  tubes  being  soaked  in  this  for  about  a 
day,  and  then  rinsed  thoroughly  and  sterilized  as 
noted  below.  In  bacteriologic  laboratories  it  is 
usual  to  cleanse  the  tubes  with  a  3  per  cent,  solu- 
tion of  sodium  hydroxid.  The  tubes  are  boiled  in 
the  solution,  rinsed,  swabbed  out  with  a  brush,  and 
allowed  to  dry  in  the  inverted  position.  A  cotton- 
wool plug  is  made  for  each  tube,  care  being  taken 
that  it  fits  neatly,  without  creases  or  channels 
and  not  too  tightly.  The  projecting  part  of  the 
plug  is  clipped  moderately  close  and  a  tinfoil  cap 
placed  on  each.  The  arrangement  is  sterilized  in 
the  hot-air  oven  at  150°  C.  When  cold,  the  tinfoil 
and  plug  are  carefully  removed,  about  10  c.c.  of 
culture-medium  put  into  each  tube,  with  as  little 
outside  contamination  as  possible,  the  plug  and 
cap  replaced,  and  the  tubes  and  contents  sterilized 
in  the  open-steam  sterilizer.  Wire  baskets  are 
used  to  hold  the  tubes  during  the  sterilizations. 

For  making  cultures  definite  volumes  of  the 
water  sample  are  introduced  into  the  culture- 
medium,  and  if  this  is  a  solidifying  form,  it  is  put 


52  ANALYTIC    OPERATIONS. 

into  the  Petri  dish.  All  the  manipulations  must 
be  conducted  with  great  care  to  avoid  contamina- 
tion. When  there  is  no  clue  to  the  amount  of 
microbes  present,  it  will  be  necessary  to  make 
cultures  with  different  proportions  of  water. 
Some  tubes  may  be  inoculated  with  a  few  drops, 
some  with  three  to  five  drops,  and  some  with  i  c.c. 
Some  operators  dilute  the  water  considerably  and 
take  small  measured  volumes.  If  this  method  is 
used,  the  diluting  water  must  be  distilled  and  have 
been  well  sterilized,  by  at  least  five  minutes'  boil- 
ing, and  cooled  out  of  contact  of  air.  All  pipets, 
dishes,  and  other  apparatus  that  come  in  contact 
with  the  water  must  have  been  first  sterilized. 

The  test-tubes  containing  the  culture-medium 
are  warmed  gently,  just  enough  to  render  the 
culture-medium  fluid,  the  desired  volume  of  the 
water  added,  the  mixture  shaken  and  promptly 
poured  into  the  petri  dishes,  covered  and  placed  in 
the  oven,  which  should  have  been  already  raised  to 
the  temperature  at  which  it  is  desired  to  conduct 
the  work.  Unless  specially  desired  otherwise, 
cultures  should  be  made  in  the  dark.  They  may 
be  made  at  any  temperature  short  of  that  at  which 
the  medium  melts,  but  either  ordinary  temperature 
or  37°  C.  is  usually  selected.  The  condition  of  the 
plates  should  be  observed  at  intervals  of  twenty- 
four  hours,  and  the  points  of  microbic  life  counted 
and  recorded.     After  some  days  the  growth  will 


SANITARY    EXAMINATIONS.  S^ 

become  ?o  luxuriant  or  the  liquefaction  of  the 
medium  so  extensive  that  accurate  observation 
is  not  possible. 

If  the  microbic  points  are  numerous,  it  will  be 
necessary  to  employ  a  counting  scale.  For  the 
petri  dish,  Pake's  modification  of  Lafar's  scale  is 
cheap  and  sufficient. 

General  Character  of  the  Microbes  in  Natural 
Waters. — The  microorganisms  of  natural  waters 
are  principally  included  in  the  genera  Bacillus  and 
Spirillum,  especially  the  former. 

Microbes  are  differentiated  to  some  extent  by 
their  action  upon  the  culture -medium.  Some 
species  rapidly  or  slowly  liquefy  the  jelly  with 
evolution  of  foul-smelling  gases;  others  produce 
characteristic  colors.  Many  do  not  produce  any 
positive  modification,  and  for  purposes  of  dis- 
tinction it  is  usual  to  transfer  portions  of  the 
colonies  to  other  culture-media.  Such  special 
cultures  are  obtained  by  taking  up  a  portion  of 
the  colony  on  the  end  of  a  wire  which  has  been 
just  sterilized  by  heating  to  redness  and  in- 
oculating the  prepared  medium. 

Indol  Reaction. — Indol,  more  properly  indin,  is 
a  nitrogenous  substance  produced  by  growth  of 
many  species  of  microbes,  and  the  detection  of  it 
may,  therefore,  be  utilized  as  a  differentiation  test. 
The  following  is  a  method  for  performing  the  test : 

Ten  c.c.  of  a  peptone  infusion,  previously  inocu- 


84  ANALYTIC    OPERATIONS. 

lated  with  the  microbes  to  be  tested,  and  kept  for 
twenty-four  hours  at  blood-heat,  are  treated  with 
I  c.c.  of  solution  of  pure  potassium  nitrite  (0.02 
gram  in  100  c.c.)  and  then  with  a  few  drops  of 
concentrated  sulfuric  acid.  In  the  presence  of 
indol  a  rose  or  deep-red  color  is  developed.  Spi- 
rillum  cholercB  and  Bacillus  coli  communis  give  the 
reaction  strongly;  5.  Finkleri  feebly;  the  so- 
called  B.  typhosus  ordinarily  does  not  give  it. 
The  reagents  and  the  culture-medium  to  be  tested 
should  be  quite  cold  and  the  mixture  should  stand 
for  about  an  hour  before  deciding  upon  the  result. 

Bacteriologists  frequently  fail  to  isolate  the 
typhoid  bacillus  from  natural  waters.  In  default 
of  a  method  for  such  detection,  resort  is  had  to 
methods  for  the  detection  of  the  microbe  known 
as  Bacillus  coli  communis  (often  called  **  colon 
bacillus'').  This  being  a  usual  inhabitant  of  the 
intestinal  canal  of  the  higher  animals,  and  being 
almost  always  associated  with  dangerous  pollu- 
tion, the  detection  of  it  in  water  indicates  previous 
contamination.  This  organism  is  not  constant  in 
character,  but,  in  common  with  many  other 
dangerous  microbes,  grows  well  at  blood-heat, 
while  many  common  water,  air,  and  soil  organisms 
do  not. 

Theobald  Smith  proposed  a  method  of  cul- 
tivating the  water  sample  at  blood-heat  with  a 
bouillon  containing  dextrose   (see  page  75)  and 


I 


SANITARY    EXAMINATIONS.  85 


noting  the  amotint  of  gas  evolved.  The  operation 
is  carried  out  in  a  tube  similar  to  that  used  in  the 
fermentation  test  for  sugar  in  urine,  but  slightly 
larger.  The  upright  part  of  the  tube  should  have 
a  capacity  of  about  15  c.c,  and  the  bulb  should  be 
nearly  4  centimeters  in  diameter.  In  judging  of 
the  amount  of  gas  produced,  the  tube  must  be 
allowed  to  stand  for  at  least  half  an  hour  at 
room-temperature,  as  the  volume  is  much  in- 
creased by  even  slight  heating.  Sufficient  bouillon 
is  put  in  to  fill  the  upright  stem  and  the  curved 
part,  but  very  little  of  the  bulb.  The  whole  is 
then  well  sterilized  in  the  steam  sterilizer,  a 
cotton  plug  with  tinfoil  cover  having  been 
previously  placed  in  the  opening  of  the  bulb. 
The  apparatus  is  cooled ;  a  few  drops  of  the  water 
sample  are  introduced  into  the  bouillon,  taking 
care  not  to  allow  outside  contamination,  the  plug 
and  tinfoil  are  replaced,  and  the  tube  kept  at 
37°  C.  for  about  forty  hours.  An  accumulation  of 
gas  at  the  top  of  the  tube  indicates  that  microbes 
of  the  type  of  the  B.  coli  communis  are  present. 
Several  tubes  and  one  or  two  control  tubes,  that 
is,  tubes  which  are  not  inoculated  with  water, 
should  be  tried  together.  Portions  of  the  gas- 
producing  bouillon  may  be  inoculated  into  sterile 
agar  and  cultivated  at  the  same  temperature 
after  pouring  into  the  petri  dish. 

The  latest  and  apparently  the  most  satisfactory 


86  ANALYTIC    OPERATIONS. 

medium  for  the  fermentation  test  is  that  pro- 
posed by  D.  D.  Jackson.  This  is  a  mixture  of 
ox-bile  and  lactose.  Jackson  found  that  the 
inspissated  preparations  commonly  sold  are  not 
satisfactory.  Fresh  ox-bile,  however,  may  be 
filtered  and  sterilized  (Jackson  uses  the  auto- 
clave at  15  pounds  for  30  minutes),  after  which  it 
can  be  kept  for  a  long  while.  Bile  also  may  be 
filtered,  evaporated  to  dryness,  and  kept  in  this 
form.  On  an  average,  1000  c.c.  of  bile  will  yield 
no  grams  of  residue  and,  therefore,  11  grams  of 
the  residue  will  suffice  to  make  100  c.c.  of  the 
culture  solution.  One  gram  of  lactose  is  added  to 
each  100  c.c.  of  bile  solution.  The  mixture  is 
placed  in  the  fermentation  tubes  and  sterilized. 

The  gas  evolved  by  the  colon  bacillus  in  these 
media  is  principally  a  mixture  of  carbon  dioxid 
and  hydrogen  in  the  proportion  of  one  volume  of 
the  former  to  two  of  the  latter,  but  other  gases 
may  be  present  in  small  amount.  The  ratio  is  not 
always  the  same.  Attempts  to  draw  conclusions 
from  a  change  in  ratio  have  not  been  satisfactory. 
The  present  opinion  of  bacteriologists  is  that  a 
water  that  shows  marked  gas  production  with  the 
fermentation  method,  especially  the  lactose-bile 
solution,  is  contaminated  with  the  colon  bacillus 
or  closely  allied  organisms. 

It  is  customary  to  make  tests  on  different  vol- 
umes of  the  sample  to  get  an  approximation  to  the 
number   of  bacilli   present.     Thus   one   or  more 


SANITARY    EXAMINATIONS.  87 

tub.es  are  inoculated  with  i  c.c.  each  of  the  sample ; 
other  tubes  with  the  same  volume  more  or  less 
diluted.  Thus,  if  lo  c.c.  of  the  sample  are  mixed 
with  90  c.c.  of  sterilized  water  and  a  culture  tube 
inoculated  with  i  c.c.  of  this  mixture,  gas  pro- 
duction will  show  that  the  bacillus  is  present  in 
0.1  c.c.  of  the  sample.  According  to  the  same 
method  a  culture  of  cooi  c.c.  may  be  made.  If 
the  sample  is  supposed  to  contain  very  few  bacilli, 
cultures  may  be  made  with  5  c.c.  or  even  10  c.c. 
Much  attention  has  been  paid  to  the  distinct- 
ions between  the  colon  bacillus  and  the  typhoid 
bacillus.  The  following  synopsis  has  been  given 
by  Abbott : 

Characteristics.         B.  typhosus.         B.  coli  communis. 

Motility, Conspicuous.  Not  marked. 

Growth  in  gelatin,    .  Slow.  Not  very  slow. 

"         "  potato, ...  Usually  inconspicu-  Always     rapid     and 

ous.  visible. 
"         "  milk, ....  No  coagulation  ;         Acidity   and    coagu- 
no  acidity.  lations    in    forty- 
eight  hoiu-s  in  in- 
cubator   at    blood 
heat 
Growth  in  media  con- 
taining    dextrose, 
lactose,      or      su- 
crose,   No  evolution  of  gas.  Marked  evolution  of 

gas. 
Growth      in     media 
containing  lactose 

and  litmus, Colonies  pale  blue  ;  Colonies  pink  ;    sur- 

no   reddening   of       rounding   medium 
medium.  red. 

Indol  reaction  in  pep- 
tone solution  (for- 
ty-eight hours  at 
37°  C.) Rarely  present.  Always  present. 


88  ANALYTIC    OPERATIONS. 

D.  D.  Jackson  and  T.  W,  Melia  have  devised  a 
process  for  isolation  of  B,  typhosus,  taking  ad- 
vantage of  the  fact  that  when  B.  coli  communis 
and  B.  typhosus  grow  in  the  bile-lactose  medium, 
the  acid  produced  soon  acts  as  a  restraining  agent 
on  the  former,  thus  giving  opportunity  for  the 
latter  to  increase.  A  description  of  this  method 
was  presented  at  the  Winnipeg  (1908)  meeting  of 
the  American  Public  Health  Association,  and  I 
am  indebted  to  Dr.  Jackson  for  permission  to 
transcribe  from  the  manuscript,  in  advance  of 
publication,  the  method  employed.  It  is  one  of 
the  most  important  advances  in  the  sanitary  ap- 
plication of  culture  methods  made  in  recent  years. 
An  essential  point  is  upon  the  use  of  a  special  agar 
suggested  by  Hesse.     The  formula  is  as  follows: 

Dry  agar 4.5  grams. 

Peptone 10  '' 

Extract  of  beef 5  '' 

Sodium  chlorid 8.5        '' 

Distilled  water 1000  c.c. 

The  agar  must  be  dried  for  thirty  minutes  at 
105°  C.  Jackson  and  Melia  found  that  commer- 
cial agar  contains  considerable  moisture,  and  if 
weighed  in  this  condition,  the  medium  may  not  be 
of  the  proper  consistence.  It  was  also  found  that 
Liebig's  extract  was  more  satisfactory  than  others. 
The  medium  must  be  stored  in  an  ice-chest,  the 


SANITARY    EXAMINATIONS.  89 

atmosphere  of  which  is  saturated  with  moisture, 
and  the  culture  must  be  carried  out  at  37°  C,  also 
in  an  atmosphere  so  saturated. 

The  following  are  the  details  of  the  preparation 
of  the  medium.  The  requisite  amount  of  the 
dried  agar  is  dissolved  in  500  c.c.  of  water  by 
heating  over  a  free  flame.  In  another  vessel  the 
peptone,  salt,  and  meat  extract  are  dissolved  in 
the  remaining  water  by  the  aid  of  heat.  The  two 
solutions  are  mixed,  boiled  for  thirty  minutes, 
cooled  somewhat,  the  loss  by  the  different  boilings 
made  up  by  adding  distilled  water,  and  the  liquid 
filtered  thru  absorbent  cotton  held'  in  the  funnel 
by  cotton  flannel.  The  liquid  should  be  clear, 
and  may  require  more  than  one  filtration  to  se- 
cure this.  The  medium  should  be  adjusted  in 
reaction  to  not  more  than  1%  normal  acid  (see 
page  75).  The  medium  should  be  distributed  in 
tubes  containing  10  c.c.  each,  sterilized  at  120°  C. 
(15  pounds)  for  twenty  minutes.  When  the  auto- 
clave can  be  opened,  the  tubes  should  be  cooled  as 
quickly  as  possible  in  running  water,  and  stored, 
as  noted  above,  in  a  cold  atmosphere  saturated 
with  moisture. 

The  test  is  carried  out  as  follows :  The  sample  to 
be  examined  is  cultivated  for  at  least  twenty-four 
hours  in  the  bile-lactose  medium  (see  page  86). 
Eight  tubes,  each  containing  9  c.c.  of  sterilized  dis- 
tilled water,  are  arranged  in  a  rack  in  convenient 


90  ANALYTIC    OPERATIONS. 

relation  with  eight  petri  dishes,  each  set  being  num- 
bered consecutively.  In  tube  i  is  placed  i  c.c.  of 
bile-lactose  culture.  The  contents  of  tube  i  are 
well  mixed,  and  i  c.c.  of  the  liquid  is  placed  in 
dish  I,  and  i  c.c.  in  tube  2.  The  contents  of  tube 
2  are  mixed,  i  c.c.  transferred  from  tube  2  to 
dish  2  and  i  c.c.  to  tube  3.  The  dilution  is  thus 
carried  out  until  the  series  is  completed.  Each 
dish  is  then  charged  with  10  c.c.  of  Hesse  agar, 
which  has  been  melted  and  cooled  to  40°  C,  the 
contents  of  each  dish  well  mixed,  all  the  dishes 
chilled  in  the  ice-chest  until  the  contents  are  solid, 
and  then  incubated  in  a  moist  atmosphere  for 
twenty-four  hours  at  37°  C. 

By  this  method,  characteristic  growths  are  ob- 
tained from  B.  typhosus,  but  only  when  the  dilu- 
tion is  high  enough  to  give  but  few  colonies  to  a 
dish.  It  is  distinguished  from  B.  colt  communis 
by  forming  colonies  of  much  larger  size,  often 
several  centimeters  in  diameter,  showing  a  broad 
translucent  or  scarcely  turbid  zone  between  the 
white  center  and  the  narrow  white  edge.  The 
colonies  may  be  taken  off  for  identification  by 
other  cultures,  or  microscopic  examination,  accord- 
ing to  the  data  on  page  87. 


TECHNIC    EXAMINATIONS.  9I 

TECHNIC  EXAMINATIONS. 

GENERAL  QUANTITATIVE  ANALYSIS. 

Silica,  Iron,  Aluminmn,  Manganese,  Calcium, 
and  Magnesium. — looo  c.c.  of  the  water  slightly 
acidified  with  hydrochloric  acid  are  evaporated  to 
complete  dryness,  best  in  a  platinum  dish,  the 
residue  treated  with  hydrochloric  acid  and  water, 
and  the  separated  silica  filtered,  washed,  dried, 
ignited  in  a  platinum  crucible,  and  weighed. 

To  the  filtrate,  previously  boiled  with  a  few 
drops  of  strong  nitric  acid,  slight  excess  of  am- 
monium hydroxid  is  added,  the  liquid  boiled 
several  minutes,  the  precipitate  collected,  washed 
thoroughly  with  boiling  water,  dried,  ignited,  and 
weighed.  It  consists  chiefly  of  FCjOgand  AI3O3, 
contains  all  the  phosphates  and  some  manganese 
if  much  is  present  in  the  water.  In  such  cases  the 
precipitate  before  drying  is  redissolved  in  hydro- 
chloric acid  and  neutralized  with  a  dilute  solution 
of  ammonium  carbonate  until  the  water  becomes 
almost  turbid.  It  is  then  boiled,  and  the  precipi- 
tate, now  free  from  manganese,  washed,  dried, 
ignited,  and  weighed.  The  iron  may  be  deter- 
mined by  dissolving  the  precipitate  in  strong 
hydrochloric  acid  and  employing  the  colorimetric 
method  described  on  page  57. 

If  no  manganese  or  only  traces  are  present,  the 


92  ANALYTIC    OPERATIONS. 

filtrate  from  the  iron  is  mixed  with  sufficient  am- 
monium chlorid  to  prevent  the  precipitation  of  the 
magnesium  ammonium  hydroxid,  and  then  am- 
moniura  oxalate  added  in  quantity  sufficient  to 
precipitate  the  calcium  and  to  convert  all  the 
magnesium  into  oxalate,  and  thus  hold  it  in  solu- 
tion. The  precipitate  contains  all  the  calcium  and 
some  of  the  magnesium.  If  the  magnesium  is 
present  only  in  relatively  small  quantity,  the 
amount  carried  down  may  be  disregarded ;  other- 
wise a  second  precipitation  should  be  made  as 
follows :  The  solution  is  allowed  to  stand  until  the 
precipitate  has  subsided;  this  will  require  some 
hours.  The  supernatant  liquid  is  poured  off 
thru  a  filter,  the  precipitate  washed  by  decantation, 
then  dissolved  in  hydrochloric  acid,  water  added, 
then  ammonium  hydroxid  and  a  small  quantity 
of  ammonium  oxalate.  After  the  calcium  oxal- 
ate has  subsided  it  is  filtered  off,  washed,  and 
dried.  If  quite  small  in  amount,  it  is  placed  with 
the  filter  in  a  weighed  platinum  crucible,  ignited 
over  the  Bunsen  burner  for  a  short  time,  and 
then  over  the  blast  lamp  for  from  five  to  fifteen 
minutes.  The  calcium  is  thus  obtained  in  the 
form  of  oxid,  which  is  allowed  to  cool  in  the 
desiccator  and  weighed.  The  weight  thus  ob- 
tained multiplied  by  0.7147  gives  the  weight  of 
calcium.  When  the  amount  of  precipitate  is 
large,  it  is  better  to  remove  it  from  the  filter  and 


TECHNIC   EXAMINATIONS.  93 

heat  it  just  short  of  redness  until  it  assumes  a 
grayish  tint.  It  then  consists  of  calcium  car- 
bonate. To  this  is  added  the  ash  of  the  filter. 
The  weight  of  the  calcium  carbonate  multiplied 
by  0.4  gives  the  weight  of  calcium. 

The  calcium  may  be  determined  by  titration. 
The  precipitate  of  calcium  oxalate,  after  thorough 
washing,  is  dissolved  from  the  filter  by  warm, 
dilute,  sulfuric  acid,  heated  to  about  65°  C,  and 
titrated  with  decinormal  permanganate  until  a 
pink  tint  is  obtained.  One  c.c.  of  the  perman- 
ganate is  equivalent  to  0.0020  calcium;  9.0028 
calcium  oxid;   0.0050  calcium  carbonate. 

The  filtrates  are  mixed,  slightly  acidified  with 
hydrochloric  acid,  concentrated  and  cooled,  am- 
monium hydroxid  and  sodium  phosphate  added 
in  excess,  stirred  briskly,  and  allowed  to  stand  in 
the  cold  for  about  twelve  hours.  The  precipitated 
ammonium  magnesium  phosphate  is  brought  upon 
a  filter,  that  adhering  to  the  sides  of  the  vessel 
being  dislodged  by  rubbing  with  a  glass  rod  tipped 
with  a  piece  of  clean  rubber  tubing.  It  is  washed 
with  a  solution  made  by  mixing  one  part  of  the 
ammonium  hydroxid  of  0.96  sp.  gr.  with  three 
parts  of  water.  The  precipitate  is  dried,  trans- 
ferred to  a  platinum  crucible,  the  filter  ashed 
separately  and  added  to  it,  and  the  whole  heated 
at  first  gently  and  then  to  intense  redness  for 
several  minutes.     After    cooling    it    is  weighed. 


94  ANALYTIC    OPERATIONS. 

It  consists  of  magnesium  pyrophosphate;  the 
weight  multipHed  by  0.2187  gives  the  weight  of 
magnesium. 

Manganese,  if  present  in  appreciable  quantity, 
is  separated  before  the  precipitation  of  the  cal- 
cium, as  follows:  The  filtrate  from  the  iron  pre- 
cipitate is  slightly  acidulated  with  hydrochloric 
acid,  concentrated,  and  the  manganese  precipi- 
tated as  sulfid  by  colorless  or  slightly  yellow  solu- 
tion of  ammonium  sulfid.  The  flask,  which  should 
be  nearly  full,  is  stoppered,  allowed  to  rest  in  a 
moderately  warm  place  until  the  precipitate  has 
thoroughly  settled,  filtered,  washed  with  dilute 
ammonium  sulfid  water,  and  purified  by  dissolv- 
ing in  a  small  quantity  of  hydrochloric  acid  and 
reprecipitating  with  ammonium  sulfid.  It  is 
filtered  off,  washed  as  before,  dried,  placed  in  a 
weighed  porcelain  crucible,  covered  with  a  little 
sulfur,  and  ignited  in  a  current  of  hydrogen  intro- 
duced into  the  crucible  by  a  tube  passing  thru  a 
hole  in  the  cover.  The  pure  manganese  sulfid 
thus  obtained  is  allowed  to  cool  and  weighed. 
The  weight  multiplied  by  0.631  gives  manganese. 

Sulfates. — Five  hundred  c.c.  of  the  clear  water 
are  slightly  acidulated  with  hydrochloric  acid, 
heated  to  boiling,  and  barium  chlorid  solution 
added  in  moderate  excess.  The  precipitated 
barium  sulfate  is  allowed  to  subside  completely, 
collected  upon  a    filter,  washed    thoroly,   dried, 


TECHNIC   EXAMINATIONS.  95 

and  incinerated.  The  weight  multipHed  by  0.42 
gives  SO.  If  the  proportion  is  very  low,  it  will  be 
advisable  to  concentrate  the  water  to  one-fifth  or 
one-tenth  its  bulk  before  precipitating. 

Control.  Potassium,  Sodium,  and  Lithium. — 
From  250  to  looo  c.c.  of  the  water,  according  to 
the  amount  of  solid  matters  present,  are  evapo- 
rated to  dryness  in  a  platinum  dish,  and  the  residue 
treated  with  a  small  amount  of  water  and  suffi- 
cient dilute  sulfuric  acid  to  decompose  the  salts 
present.  The  dish  should  then  be  covered  and 
placed  upon  the  water-bath  for  five  or  ten  minutes, 
after  which  any  liquid  spurted  on  the  cover  is 
washed  into  the  dish,  the  whole  evaporated  to 
dryness  and  heated  to  redness.  A  few  drops  of 
ammonium  carbonate  solution  should  then  be 
mixed  with  the  residue,  and  the  ignition  repeated 
to  insure  the  removal  of  the  last  portions  of  free 
acid.  In  the  ifiajority  of  cases  the  only  basic 
elements  present  in  considerable  quantity  are 
calcium,  magnesium,  and  sodium.  The  sodium 
may  be  determined  indirectly,  therefore,  by  cal- 
culating from  the  amount  of  calcium  and  mag- 
nesium found,  the  calcium  and  magnesium  sulfate 
in  the  residue,  and  subtracting  this  sum,  together 
with  the  silica,  from  the  total  residue. 

For  the  determination  of  potassium  and  sodium 
in  ordinary  well  and  river  waters,  not  less  than 
2000  c.c.  should  be  employed.     When  lithium  is 


96  ANALYTIC    OPERATIONS. 

to  be  determined,  it  is  generally  necessary  to  use 
much  more.  In  any  case,  as  the  alkalis  are  to  be 
weighed  as  chlorids,  it  is  advisable,  if  notable 
amounts  of  sulfates  are  present,  to  precipitate 
them  by  addition  of  barium  chlorid. 

The  water  is  evaporated  to  about  200  c.c,  a 
slight  excess  of  pure  calcium  hydroxid  added  to 
the  hot  liquid, — generally  a  few  c.c.  of  thin  milk  of 
lime  will  be  sufficient, — and  the  heat  continued 
for  several  minutes.  It  is  then  washed  into  a 
250  c.c.  flask,  disregarding  the  insoluble  portion 
adhering  to  the  dish,  which,  however,  should  be 
thoroly  washed,  and  the  washings  added  to  the 
flask.  After  cooling,  the  flask  is  filled  up  to  the 
mark  with  distilled  water,  thoroly  mixed,  the 
precipitate  allowed  to  settle,  and  the  liquid  fil- 
tered thru  a  dry  filter.  Two  hundred  c.c.  of  the 
filtrate  are  measured  into  another  250  c.c.  flask, 
ammonium  carbonate  •  and  ammonium  oxalate 
added,  filled  with  water  up  to  the  mark,  mixed, 
allowed  to  settle,  filtered  thru  a  dry  filter,  200 
c.c.  of  the  filtrate  measured  off,  and  evaporated 
to  complete  dryness  in  a  platinum  crucible,  heating 
very  cautiously  at  the  last  stages,  to  avoid  loss 
by  spurting.  The  low-temperature  burner  is 
suited  for  this  purpose.  The  crucible  is  now 
covered  and  cautiously  heated  to  dull  redness, 
cooled,  and  weighed.  The  residue  contains  the 
potassium,  lithium,  and  sodium  as  chlorids.     It 


TECHNIC    EXAMINATIONS.  97 

contains,  sometimes,  also,  traces  of  magnesium, 
which  may  be  removed  by  treating  again  with 
lime  and  ammonium  carbonate  and  oxalate.  It 
is  frequently  of  advantage,  in  evaporating  these 
saline  solutions,  to  add,  when  the  solution  be- 
comes Concentrated,  several  cubic  centimeters  of 
strong  hydrochloric  acid.  This  precipitates  the 
greater  portion  of  the  salts  in  a  finely  granular 
condition,  and  renders  loss  by  spurting  less  liable 
to  occur. 

If  potassium  and  sodium  chlorids  only  are 
present,  the  residue  is  dissolved  in  a  small  quan- 
tity of  water,  an  excess  of  a  concentrated  neutral 
solution  of  platinum  chlorid  added,  evaporated  to 
small  bulk  at  a  low  heat  on  the  water-bath,  some 
eighty  per  cent,  alcohol  added,  allowed  to  stand, 
the  clear  liquid  decanted  off  on  a  small  filter,  and 
the  residue  washed  in  this  way  several  times  by 
fresh,  small  portions  of  eighty  per  cent,  alcohol. 
The  precipitate  is  then  washed  on  to  the  filter 
with  alcohol,  washed  again  with  eighty  per  cent, 
alcohol,  dried  well,  and  transferred  as  far  as 
possible  to  a  watch-glass.  The  small  portion  on 
the  filter  is  dissolved  off  and  the  solution  placed  in 
a  weighed  platinum  dish  and  evaporated  to  dry- 
ness. The  main  portion  on  the  watch-glass  is 
then  added,  and  the  whole  dried  to  a  constant 
weight  at  about  260°  F.,  cooled,  and  weighed. 
The  weight  thus  found,  multiplied  by  0.307,  gives 
7 


98  ANALYTIC    OPERATIONS. 

the  weight  of  potassium  chlorid.  This,  subtracted 
from  the  combined  weight  of  the  chlorids,  gives  the 
weight  of  sodium  chlorid. 

Lithium,  if  present,  is  best  separated  before 
the  treatment  with  platinum  chlorid.  The  follow- 
ing method,  devised  by  Grooch,  gives  good  re- 
sults :  To  the  concentrated  solution  of  the  weighed 
chlorids,  amyl  alcohol  is  added  and  heat  applied, 
gently  at  first,  to  avoid  bumping,  until  the  water 
disappears  from  the  solution  and  the  point  of 
ebullition  becomes  constant  at  a  temperature 
which  is  approximately  that  at  which  the  alcohol 
boils  (182°  C),  the  potassium  and  sodium  chlorids 
are  deposited,  and  the  lithium  chlorid  is  dehy- 
drated and  taken  into  solution.  The  liquid  is 
then  cooled,  and  a  drop  or  two  of  strong  hydro- 
chloric acid  added  to  reconvert  traces  of  lithium 
hydroxid  in  the  deposit  and  the  boiling  continued 
until  the  alcohol  is  again  free  from  water.  If  the 
amount  of  lithium  chlorid  be  small,  it  will  be 
found  in  the  solution  and  the  potassium  chlorid 
and  sodium  chlorid  in  the  residue,  excepting  traces 
which  can  be  allowed  for.  If  the  lithium  chlorid 
exceed  ten  or  twenty  milligrams,  the  liquid  may 
be  decanted,  the  residue  washed  with  amyl  alco- 
hol, dissolved  in  a  few  drops  of  water,  and  treated 
as  before.  For  washing,  amyl  alcohol,  previ- 
ously dehydrated  by  boiling,  is  to  be  used  and 
the  filtrates  are  to  be  measured  apart  from  the 


TECHNIC   EXAMINATIONS.  99 

washings.  In  filtering,  the  Gooch  filter  with 
asbestos  felt  may  be  used  with  advantage,  apply- 
ing gentle  pressure  by  the  aid  of  the  filter-pump. 
The  crucible  and  residue  are  ready  for  weighing 
after  gentle  heating  over  the  low-temperature 
burner.  The  weight  of  the  insoluble  chlorids  is 
to  be  corrected  by  adding  0.00041  for  every  10  c.c. 
of  amyl  alcohol  in  the  filtrate,  exclusive  of  the 
washings,  if  only  sodium  chlorid  be  present; 
0.00051  for  every  10  c.c.  if  only  potassium  chlorid, 
and  0.00092  in  the  presence  of  both  these  chlorids. 

The  filtrate  and  washings  are  evaporated  to 
dryness  in  a  platinum  crucible  heated  with  sul- 
furic acid,  the  excess  driven  off,  and  the  residue 
ignited  to  fusion,  cooled,  and  weighed.  From 
the  weight  is  to  be  subtracted,  for  each  10  c.c.  of 
filtrate,  0.0005,  0.00059,  ^^  0.00109,  according  as 
only  sodium  chlorid,  potassium  chlorid,  or  both 
were  present  in  the  original  mixture. 

Hydrogen    Sulfid. — The    following    method    is 
taken  from  Sutton's  ''Volumetric  Analysis'': 
Reagents  Required : 

Centinormal  lodin. — Dry,  commercial  iodin  is 
intimately  mixed  with  one-fourth  its  weight  of 
pure  potassium  iodid  and  gently  heated  between 
two  clock-glasses  by  resting  the  lower  on  a  hot 
plate.  The  iodin  sublimes  in  a  perfectly  pure 
condition.  It  is  allowed  to  cool  under  the  desic- 
cator,  1.2797  grams  weighed  out,  together  with 


lOO  ANALYTIC    OPERATIONS. 

1.8  grams  of  pure  potassium  iodid,  dissolved  in 
about  50  c.c.  of  water,  and  the  solution  made  up 
exactly  to  1000  c.c.  The  liquid  must  not  be 
heated,  and  care  should  be  taken  that  no  iodin 
vapor  is  lost.  One  c.c.  is  equivalent  to  0.00017 
H2S.  The  solution  is  best  prepared  in  stoppered 
bottles,  which  should  be  completely  filled  and 
kept  in  the  dark.  It  will  not  even  then  keep  very- 
long,  and  should  be  standardized  by  titration 
with  a  weighed  amount  of  pure  sodium  thiosulfate, 
which  should  be  powdered  previous  to  weighing, 
and  pressed  between  filter-paper  to  absorb  any 
moisture.  Fifty  c.c.  of  the  iodin  solution,  when 
of  full  strength,  will  require  0.124  gram  of  sodium 
thiosulfate. 

Starch  Indicator. — See  page  47. 
Analytic  Process : 

Ten  c.c,  or  any  other  necessary  volume  of  the 
iodin  solution,  is  measured  into  a  500  c.c.  flask, 
and  the  water  to  be  examined  added  until  the 
color  disappears.  Five  c.c.  of  starch  liquor  are 
then  added,  and  the  iodin  solution  run  in  until  the 
blue  copper  appears;  the  flask  is  then  filled "tb  the 
mark  with  distilled  water.  The  respective  vol- 
umes of  iodin  and  starch  solution,  together  with 
the  added  water,  deducted  from  the  500  c.c,  will 
show  the  volume  of  water  actually  titrated  by 
iodin.  A  correction  should  be  made  as  follows  for 
the  excess  of  iodin  required  to  produce  the  blue 


TECHNIC    EXAMINATIONS.  lOI 

color:  Five  c.c.  starch  solution  are  made  up  with 
distilled  water  to  500  c.c,  iodin  run  in  until  the 
color  matches  that  in  the  test,  and  the  volume  of 
iodin  solution  so  used  subtracted  from  the  figure 
obtained  in  the  first  titration. 

Hardness.  CO  3  in  Normal  Carbonates. — Waters 
containing  considerable  quantities  of  calcium  and 
magnesium  are  said  to  be  hard.  Since  the  solu- 
tion of  calcium  and  magnesium  carbonate  in  water 
depends  partly  upon  the  presence  of  carbon 
dioxid,  boiling  precipitates  the  greater  portion  of 
the  carbonates,  the  result  being  to  diminish  the 
hardness — i,  e.,  to  soften  the  water.  Magnesium 
and  calcium  sulfates  and  chlorids  are  not  precipi- 
tated in  this  way.  Hardness,  therefore,  is  divided 
into  two  classes,  temporary  and  permanent,  the 
former  being  that  which  may  be  removed  by 
boiling.  The  determination  may  be  made  by 
titration  with  acid  or  soap  solution. 

Acid  Titration  Method. — This  method  is  due 
to  Hehner.  His  description  is  followed,  but 
there  seems  to  be  no  reason  why  the  standard 
acid  can  not  be  made  by  diluting  decinormal  acid 
with  three  times  its  bulk  of  water.  It  would  also 
be  advisable  to  try  the  alizarin  indicator  (see  p.  15) 
in  place  of  methyl  orange. 
Reagents  Required : 

Standard  Sodium  Carbonate. — 1.061  grams  of 
recently  ignited  pure  sodium  carbonate  are  dis- 


I02  ANALYTIC    OPERATIONS. 

solved  in  water  and  the  solution  diluted  to  looo 
c.c.  One  c.c.  =  0.00106  gram  Na2C03,  equiv- 
alent to  o.ooi  gram  CaCOg. 

Standard  Sulfuric  Acid. — One  c.c.  of  pure  con- 
centrated sulfuric  acid  is  added  to  about  1000  c.c. 
of  water.  Fifty  c.c.  of  the  standard  sodium  car- 
bonate are  placed  in  a  porcelain  dish,  heated  to 
boiling,  a  few  drops  of  a  solution  of  methyl  orange 
added,  and  the  sulfuric  acid  cautiously  run  in 
from  a  buret  until  the  proper  change  of  color 
occurs.  From  the  figure  thus  obtained,  the  ex- 
tent to  which  the  acid  should  be  diluted  in  order 
to  make  i  c.c.  of  the  sodium  carbonate  equivalent 
to  I  c.c.  of  the  acid  may  be  calculated.  The 
proper  amount  of  water  is  then  added,  and  the 
solution  verified  by  again  titrating. 
Analytic  Process : 

Temporary  Hardness. — One  hundred  c.c.  to 
250  c.c.  of  the  water  tinted  with  the  indicator  are 
heated  to  boiling,  and  the  sulfuric  acid  cautiously 
run  in  until  the  color-change  occurs.  Each  cubic 
centimeter  required  will  represent  one  part  of 
calcium  carbonate  or  its  equivalent  per  100,000 
parts  of  the  water. 

Permanent  Hardness, — To  100  c.c.  of  the  water 
is  added  an  amount  of  the  sodium  carbonate 
solution  more  than  sufficient  to  decompose  the 
calcium  and  magnesium  sulfates,  chlorids,  and 
nitrates   present;    usually   a   bulk  equal   to   the 


TECHNIC    EXAMINATIONS.  IO3 

water  taken  will  be  more  than  sufficient.  The 
mixture  is  evaporated  to  dryness  in  a  nickel  or 
platinum  dish,  and  the  residue  extracted  with 
distilled  water.  The  solution  is  filtered  thru  a 
very  small  filter,  and  the  filtrate  and  washings 
titrated  hot  with  sulfuric  acid  as  above;  or  25 
c.c.  of  distilled  water  may  be  poured  on  the  residue, 
and  the  solution  obtained  filtered  thru  a  dry  filter, 
the  filtrate  measured  and  titrated.  The  difference 
between  the  number  of  cubic  centimeters  of 
sodium  carbonate  used  and  the  acid  required  for 
the  residue  will  give  the  permanent  hardness. 

If  the  water  contains  sodium  or  potassium  car- 
bonate, there  will  be  no  permanent  hardness,  and 
there  will  be  more  acid  required  for  the  filtrate 
than  the  equivalent  of  the  sodium  carbonate 
added.  From  this  excess  the  quantity  of  sodium 
carbonate  in  the  water  may  be  determined. 

Since  any  alkali  carbonate  in  the  water  would  be 
erroneously  calculated  as  temporary  hardness  by 
the  direct  titration,  the  equivalent,  in  terms  of 
calcium  carbonate,  of  the  alkali  carbonate  present 
should  be  deducted  from  the  figure  given  by  the 
titration  in  order  to  get  the  true  temporary  hard- 
ness. 

The  total  CO  3  in  normal  carbonates  is  given  by 
the  direct  titration  of  the  water  with  dilute  sulfuric 
acid.  One  c.c.  of  the  acid  is  equivalent  to  0.0006 
gram  of  CO3. 


I04  ANALYTIC    OPERATIONS. 

Soap  Titration  Method. — This  is  done  with 
a  solution  of  soap  in  dilute  alcohol.  Commercial 
soap  is  irregular  in  composition,  even  apart  from 
intentional  adulteration.  '' Castile"  soap  is  re- 
commended, but  it  must  be  borne  in  mind  that 
this  title  has  now  no  positive  value.  Good  soaps 
can  be  obtained  from  responsible  dealers.  Trans- 
parent or  dark  soaps  should  not  be  used. 

The  following  method  has  been  used  largely  in 
the  laboratory  of  the  State  Board  of  Health  of 
Massachusetts  and  will  be  found  satisfactory. 
Reagents  Required : 

Standard  Calcium  Chlorid  Solution. — 0.2  gram  of 
pure  calcium  carbonate  is  dissolved  in  dilute 
hydrochloric  acid  in  a  porcelain  dish,  the  solution 
evaporated  to  dryness,  redissolved  and  reevapor- 
ated,  until  a  perfectly  neutral  salt  remains. 
This  is  dissolved  in  water  and  made  up  to 
1000  c.c.  One  c.c.  contains  calcium  equivalent 
to  0.0002  gram  calcium  carbonate. 

Soap  Solution. — Castile  soap  is  cut  into  thin 
shavings,  dried,  10  grams  weighed  out  and  dis- 
solved in  a  mixture  of  fifty  c.c.  of  alcohol  (95%) 
and  50  c.c.  of  water,  and  the  solution  allowed  to 
settle  over  night.  Fifty  c.c.  of  it  should  be  diluted 
to  1000  c.c.  principally  with  water,  but  using  enough 
alcohol  to  prevent  soap  separating.  The  liquid 
may  be  slightly  turbid,  in  which  case  it  may  be 
filtered.     As   alcohol   and   water   produce    slight 


TECHNIC    EXAMINATIONS.  10$ 

contraction  when  mixed,  the  solution  will  contain 
a  little  over  5  grams  to  1000  c.c.  Fifty  c.c.  of 
the  standard  solution  of  calcium  chlorid,  which, 
according  to  the  table,  should  take  exactly  14.25 
c.c.  of  standard  soap,  are  used  to  test  the  strength. 
The  soap  solution  thus  prepared  does  not  change 
perceptibly  if  air  fias  no  access  to  it,  and,  if  used 
with  a  siphon  buret  attached  to  the  bottle,  will 
keep  for  five  or  six  weeks  or  longer. 

For  the  standardization  of  the  soap,  and  for  the 
determination  of  the  hardness  of  any  water, 
50  c.c.  of  the  sample  or  of  the  standard  calcium 
chlorid  solution  are  placed  in  a  flask  or  bottle  of 
200  c.c.  capacity,  and  of  a  convenient  shape,  and 
the  soap  solution  added,  0.2  or  0.3  c.c.  at  a 
time,  shaking  well  after  each  addition,  until  a 
lather  is  obtained  which  is  permanent  for  five 
minutes  and  covers  the  entire  surface  of  the  liquid 
with  the  bottle  placed  on  its  side. 

The  soap  solution  must  be  added  in  small 
quantities,  especially  in  the  presence  of  mag- 
nesium compounds.  If  much  carbonic  acid  is 
liberated,  it  is  well  to  remove  it  by  suction.  The 
table  (page  106)  does  not  apply  to  hardness  above 
12.5.  If  the  water  tested  requires  more  than 
10  c.c.  of  the  standard  soap  solution,  a  smaller 
portion  of  25  c.c,  10  c.c,  or  even  2  c.c,  as  the 
case  may  require,  is  measured  out  and  made  up  to 
a  volume  of  50  c.c  with  recently  distilled  water. 


io6 


ANALYTIC    OPERATIONS. 


This  will  keep  the  results  comparable  with  each 
other,  altho  the  dilution  introduces  some  error 
into  the  calculation. 

The  following  table  gives  the  hardness  cor- 
responding to  the  number  of  cubic  centimeters  of 
soap  solution  used  in  the  analyses : 


C.C.  OF 

C.C.   OF 

C.C.  OF 

Soap 

Soap 

Soap 

Solu- 

Hard- 

Solu- 

Hard- 

Solu- 

Har 

tion. 

ness. 

tion. 

ness. 

tion. 

NESS 

0.7 

0.0 

-       3.7 

4.1 

6.7 

8.4 

0.8 

0.1 

3.8 

4.2 

6.8 

8.5 

0.9 

0.3 

3.9 

4.4 

6.9 

8.7 

I.O 

0.4 

4.0 

4.5 

7.0 

8.8 

I.I 

0.6 

4.1 

4-7 

7.1 

9.0 

1.2 

0.7 

4.2 

4.8 

7.2 

9.1 

1.3 

0.9 

4.3 

5.0 

7.3 

9.2 

1.4 

I.I 

4.4 

5.1 

7.4 

9.4 

1.5 

1.2 

4.5 

5.2 

7.5 

9.5 

1.6 

1.4 

4.6 

5.4 

7.6 

9.7 

1.7 

1.5 

4.7 

5.5 

7.7 

9.8 

1.8 

1.6 

4.8 

5.7 

7.8 

lO.O 

1.9 

1.8 

4.9 

5.8 

7.9 

lO.I 

2.0 

1.9 

5.0 

6.0 

8.0 

10.3 

2.1 

2.0 

5.1 

6.1 

8.1 

10.4 

2.2 

2.2 

5.2 

6.2 

8.2 

10.6 

2.3 

2.3 

5.3 

6.4 

8.3 

10.7 

2.4 

2.4 

5.4 

6.5 

8.4 

10.9 

2.5 

2.6 

5.5 

6.7 

8.5 

II. 0 

2.6 

2.7 

5.6 

6.8 

8.6 

II. 2 

2.7 

2.8 

5.7 

7.0 

8.7 

II-3 

2.8 

2.9 

5.8 

7.1 

8.8 

11.5 

2.9 

3.1 

5.9 

7.2 

8.9 

11.6 

3.0 

3.2 

6.0 

7.4 

9.0 

11.8 

3.1 

3.3 

6.1 

7.5 

9.1 

11.9 

3.2 

3.5 

6.2 

7.7 

9.2 

12.1 

3.3 

3.6 

6.3 

7.8 

9-3 

12.2 

3.4 

3.7 

6.4 

8.0 

9.4 

12.4 

3.5 

3.9 

6.5 

8.1 

9.5 

12.5 

3.6 

4.0 

6.6 

8.2 

TECHNIC    EXAMINATIONS.  107 

If  the  hardness  of  a  water  is  given  as  9.0,  it 
means  that  in  100,000  pounds  of  water  there  is  of 
calcium  and  magnesium  salts  a  quantity  which 
gives  the  same  hardness  to  water  which  would  be 
given  by  nine  pounds  of  calcium  carbonate.  In 
order  to  soften  this  water  for  manufacturing 
purposes,  about  nine  pounds  of  soda  ash  will  be 
required,  and  for  laundry  purposes  about  ninety 
pounds  of  soap. 

Free  and  Half-bound  Carbonic  Acid. — Several 
methods  for  the  determination  of  these  data  have 
been  devised.  Pettenkofer's  is  much  used,  but 
F.  B.  Forbes  and  G.  H.  Pratt,  after  careful  study 
of  different  methods,  favor  the  Lunge-Trillich 
(also  termed  the  Seyler)  method,  which  they 
describe  as  follows : 

One  hundred  c.c.  of  the  sample  are  placed  in  a 
tall  glass  cylinder,  by  means  of  a  siphon  (in  order 
to  avoid  contact  with  air),  6  drops  of  neutral 
alcoholic  solution  of  phenolphthalein  added,  and 
^/so  sodium  carbonate  run  in  from  a  buret  with 
careful  stirring,  until  a  faint  permanent  pink  is 
obtained.  If  the  water  contains  much  free  car- 
bonic acid,  it  is  better  to  take  less  than  100  c.c, 
and  in  every  case  care  must  be  taken  not  to  stir 
the  sample  so  vigorously  as  to  cause  loss  of  the 
acid,  nor  to  proceed  so  slowly  that  it  may  be  ab- 
sorbed from  the  air.  The  solutions  must  be  ca^- 
fuUy  standardized  and  preserved  so  that  they  do 


Io8  ANALYTIC    OPERATIONS. 

not  absorb  the  acid.  The  fixed  carbonic  acid  is 
determined  on  another  portion  of  the  sample  by 
Hehner's  method,  as  given  above.  In  waters  acid 
to  phenolphthalein  this  will  be  equal  to  the  half- 
bound. 

When  the  water  is  alkaline  to  phenolphthalein, 
the  alkalinity  with  this  indicator  is  first  deter- 
mined, then  the  total  alkalinity  by  Hehner's 
method.  Twice  the  phenolphthalein  alkalinity 
subtracted  from  the  total  alkalinity  gives  the  half- 
bound  acid,  no  free  acid  being  present  in  this  case, 
and  the  half-bound  being  less  than  the  fixed. 
If  the  water  is  neutral  to  phenolphthalein,  the 
half -bound  may  be  equal  to  the  fixed. 

Forbes  and  Pratt  have  modified  the  Pettenkofer 
methods  as  follows : 

Ground-glass-stoppered  bottles,  holding  ap- 
proximately 480  c.c,  are  accurately  calibrated  by 
weighing  completely  filled  with  water.  The  bottle 
is  filled  with  the  water  to  be  analyzed  by  means  of 
a  siphon,  the  glass  stopper  inserted,  leaving  no 
air-bubble,  and  the  neck  of  the  bottle  wiped  dry. 
The  glass  stopper  is  then  carefully  removed,  and 
the  57  c.c.  of  the  water  withdrawn  by  means  of  an 
accurately  calibrated  pipet,  in  order  to  make  room 
for  the  reagents.  Three  c.c.  of  strong  barium 
chlorid  solution  (8  grams  per  liter),  2  c.c.  of  sat- 
urated ammonium  chlorid  solution,  and  50  c.c. 
of  standard  barium  hydroxid  are  then  introduced, 


TECHNIC    EXAMINATIONS.  I09 

the  bottle  quickly  stoppered,  well  shaken,  and 
set  aside  to  settle. 

There  is  now  in  the  bottle  an  air  space  of  only 
2  C.C.,  which  is  left  to  avoid  the  possibility  of  loss 
of  liquid  when  the  stopper  is  inserted.  After  the 
precipitated  carbonates  have  completely  settled 
out,  several  portions  of  loo  c.c.  are  siphoned  off  and 
titrated,  with  ^/s©  sulfuric  acid,  which  is  prepared 
from  decinormal  acid,  against  which  the  barium 
hydroxid  is  standardized,  by  carefully  diluting 
with  water  freed  from  carbonic  acid  by  boiling. 
The  barium  hydroxid  used  is  approximately 
^/is,  and  is  carefully  preserved  out  of  contact  with 
the  air,  the  bottle  in  which  it  is  kept  being  fitted 
with  an  arrangement  whereby  the  air  is  drawn 
through  soda-lime  before  entering  either  the 
bottle  or  the  buret.  The  figure  obtained  by 
averaging  several  results  of  titration  of  portions  of 
100  c.c.  is  taken  as  the  true  value. 

The  use  of  this  large  quantity  of  water  and  the 
titration  of  loo  c.c.  portions  reduce  considerably 
the  errors  due  to  the  difficulty  of  obtaining  the 
exact  end-point,  and  those  due  to  inaccuracies  of 
measurement. 

Boric  Acid. — To  detect  this,  add  to  looo  c.c.  of 
the  water  sufficient  sodium  carbonate  to  render  it 
distinctly  alkaline.  Evaporate  to  dryness,  acidify 
with  hydrochloric  acid,  moisten  a  slip  of  turmeric 
paper  with  the  liquid,  and  dry  it  at  a  moderate 


no  ANALYTIC   OPERATIONS. 

heat.  In  the  presence  of  boric  acid  the  paper  will 
assume  a  distinct  brown-red  tint. 

Analysis  of  Boiler  Scale. — If  the  scale  is  made  up 
of  pieces  of  decidedly  different  quality,  some  being 
hard  and  gritty,  others  soft  and  friable,  separate 
tests  should  be  made  on  representative  samples  of 
each  sort;  but  if  the  general  character  is  fairly 
uniform,  it  will  be  sufficient  to  sample  the  entire 
mass  and  reduce  about  5  grams  to  a  fine  powder, 
finishing  in  an  agate  mortar.  All  of  the  quantity 
selected  as  the  sample  should  be  equally  finely 
powdered. 

0.5  gram  should  be  heated  in  a  covered  beaker 
with  moderately  strong  hydrochloric  acid,  until 
all  soluble  matter  is  dissolved;  the  liquid  is  then 
evaporated  to  dryness  on  the  water-bath,  re- 
dissolved  in  water  containing  some  hydrochloric 
acid,  and  filtered.  The  precipitate  is  silica.  The 
filtrate  and  washings  are  mixed  and  divided  into 
convenient  parts.  One  part  is  used  for  the  de- 
termination of  sulfates,  and  the  other  for  iron 
oxid,  alumina,  calcium,  and  magnesium,  accord- 
ing to  the  methods  given  on  pages  91-5.  Scale 
often  contains  an  appreciable  amount  of  oil. 
This  may  be  determined  by  extracting  a  known 
weight  of  the  finely  powdered  material  with  a 
petroleum  spirit  that  leaves  no  residue  on  evapora- 
tion on  the  water-bath. 


TECHNIC   EXAMINATIONS. 


Ill 


SPECTROSCOPIC  EXAMINATION. 

For  the  ordinary  spectroscopic  examination  of 
a   water   a   simple    apparatus   will   suffice.     The 
arrangement  shown  in  the  cut  (Fig.  13)  is  a- small 
direct-vision    s  p  e  c  t  r  o- 
scope,   held    in    a    uni- 
versal  stand,    with    an 
adjustable  burner  as  the 
source  of  heat. 

For  the  examination 
1000  c.c.  or  more  should 
be  evaporated  nearly  to 
dryness,  a  little  hydro- 
chloric acid  being  added 
near  the  end  of  the  pro- 
cess, the  residue  placed 
in  a  narrow  strip  of 
platinum  foil,  having] 
the  sides  bent  so  as  to 
retain  the  liquid,  and 
heated  in  the  flame. 
While  this  method  will 
be  sufficient  in  many 
cases,  a  far  better  plan 
is  to  separate  the  substance  sought  for  in  a 
state  of  approximate  purity  and  then  examine 
with  the  spectroscope.  Very  small  traces  of 
lithium,  for  instance,  may  be  detected  as  follows: 


Fig.  13. 


112  ANALYTIC    OPERATIONS. 

To  about  I  GOO  c.c.  of  the  water  sufficient  sodium 
carbonate  is  added  to  precipitate  all  the  calcium 
and  magnesium,  and  the  liquid  boiled  down  to 
about  one-tenth  its  bulk;  it  is  then  filtered,  the 
filtrate  rendered  slightly  acid  with  hydrochloric 
acid,  and  evaporated  to  dryness.  The  residue  is 
boiled  with  a  little  alcohol,  which  will  dissolve  out 
the  lithium  chlorid.  The  alcoholic  solution  is 
evaporated  to  dryness,  the  residue  taken  up  with  a 
little  water  and  tested  in  the  flame. 

In  order  to  identify  with  certainty  any  line 
which  may  be  obtained,  it  is  only  necessary  to 
hold  in  the  flame  at  the  same  time  a  wire  which 
has  been  dipped  in  a  solution  of  the  substance 
supposed  to  be  present  and  to  note  whether  the 
lines  produced  by  it  and  the  material  under  ex- 
amination are  identical. 

SPECIFIC  GRAVITY. 
In  the  great  majority  of  cases  the  determination 
of  specific  gravity  is  not  essential.  Ordinary 
river,  spring,  and  well  waters  contain  such  small 
proportions  of  solid  matter  that  it  is  usually  the 
practice  to  take  a  measured  volume  and  to  assume 
its  weight  to  be  that  of  an  equal  bulk  of  pure 
water.  If  the  proportion  of  solids  be  high,  a 
determination  of  the  specific  gravity  may  be 
desirable.  For  this  purpose  the  specific  gravity 
bottle  may  be  used.     This  consists  merely  of  a 


TECHNIC    EXAMINATIONS.  II3 

small  flask  provided  with  a  finely  perforated  glass 
stopper.  The  bottle  is  weighed  first  alone,  then 
filled  with  distilled  water  at  60"^  F.,  and  finally 
with  the  water  under  examination  at  the  same 
temperature.  In  filling  the  bottle,  the  liquid  is 
first  brought  to  the  proper  temperature,  the  bottle 
completely  filled,  the  stopper  inserted,  and  the 
excess  of  water  forced  out  thru  the  perforation 
and  around  the  sides  of  the  stopper  carefully  re- 
moved by  bibulous  paper.  The  weight  of  the 
water  examined  divided  by  the  weight  of  the 
equal  bulk  of  distilled  water  at  the  same  temper- 
ature gives  the  specific  gravity. 

Another  method,  and  one  which  gives  very 
satisfactory  results,  is  by  the  use  of  a  plummet. 
This  may  conveniently  consist  of  a  piece  of  a 
thick  glass  rod  of  about  10  c.c.  in  bulk,  or  of  a 
test-tube  weighted  with  mercury  and  the  open  end 
sealed  in  the  flame.  The  plummet  is  suspended 
to  the  hook  of  the  balance  by  means  of  a  fine 
platinum  wire  and  its  weight  ascertained.  It  is 
then  immersed  in  distilled  water  at  60°  F.,  and 
the  loss  in  weight  noted.  The  figure  so  obtained 
is  the  weight  of  a  bulk  of  water  equal  to  that  of  the 
plummet.  This  having  been  determined,  the 
specific  gravity  of  any  water  may  be  found  by 
immersing  in  it  the  plummet  and  noting  the  loss  in 
weight.  This,  divided  by  the  loss  suffered  in  pure 
water,  gives  the  specific  gravity. 


INTERPRETATION  OF   RESULTS. 

STATEMENT  OF  ANALYSIS. 

The  composition  of  water  is  generally  stated 
in  terms  of  a  unit  of  weight  in  a  definite  volume  of 
liquid,  but  much  difference  exists  as  to  the  stand- 
ard used.  The  decimal  system  is  very  largely 
employed,  the  proportions  being  expressed  in 
milligrams  per  liter,  nominally  parts  per  million; 
or  in  centigrams  per  liter,  nominally  parts  per 
hundred  thousand.  The  figures  are  often  given 
in  grains  per  Imperial  gallon  of  70,000  grains,  or 
the  U.  S.  gallon  of  58,328  grains.  In  this  work  the 
composition  is  always  expressed  in  milligrams  per 
1000  c.c.  This  ratio  is  practically  equivalent  to 
parts  per  million,  except  in  case  of  water  very  rich 
in  solids,  a  1000  c.c.  of  which  will  weigh  notably 
more  than  one  million  rnilligrams.  Factors  for 
converting  the  different  ratios  are  given  at  the 
end  of  the  book. 

From  the  analysis  of  a  water  it  is  rarely  possible 
to  ascertain  the  exact  arrangement  of  the  elements 
determined,  but  it  is  the  custom  to  assume  ar- 
rangements based  upon  the  rule  of  associating  in 
combination  elements  having  the  highest  affinities, 

114 


STATEMENT    OF    ANALYSIS.  II5 

modifying  this  system  by  any  inferences  derived 
from  the  character  or  reactions  of  the  water  itself. 
It  has  been  demonstrated  that,  even  in  the  case 
of  mixtures  of  salts  producing  no  insoluble  sub- 
stances, partial  interchange  of  the  basylous  and 
acidulous  radicles  takes  place.  In  a  solution  of 
sodium  chlorid  and  potassium  sulfate,  sodium 
sulfate  and  potassium  chlorid  will  be  found,  as 
well  as  the  original  salts.  When  the  conditions 
are  rendered  more  complex  by  the  addition  of 
other  substances,  it  is  obviously  impossible  to 
determine  the  exact  arrangement.  In  view  of 
these  facts,  it  is  preferable  to  express  the  com- 
position of  a  water  by  the  proportion  of  each  ele- 
ment or  radicle  present.  '  In  this  way  a  water 
containing  sodium  chlorid  will  be  expressed  in 
terms  of  sodium  and  chlorid,  respectively.  In 
the  case  of  silica  which  may  exist  free  in  the 
water,  the  proportion  is  expressed  as  such.  It 
frequently  occurs  that  the  characteristics  of  some 
of  the  compounds  in  a  water  are  sufficiently 
marked  to  indicate  their  presence,  and  there  is 
no  objection  to  suggesting,  in  connection  with  the 
analytic  statement,  the  inferences  which  may 
thus  be  drawn. 

The  organic  matters,  or  derived  products,  are 
best  stated  in  terms  of  the  nitrogen  which  they 
contain,  thus  permitting  a  comparison  of  the 
different   stages    of   decomposition.     It   is   inad- 


Il6  INTERPRETATION    OF    RESULTS. 

visable  to  represent  the  amount  of  unchanged 
organic  matter  in  terms  of  oxalic  acid,  as  has  been 
suggested,  or  to  express  the  nitrogen  in  terms  of 
albumin,  or  any  other  supposititious  compound. 

The  results  of  microbe  counting  should,  as  a 
rule,  be  reported  as  "points  of  microbic  life"  in 
the  given  volume  of  water.  Many  operators, 
however,  report  the  number  of  points  as  *'  colonies" 
or  even  ''bacteria." 

SANITARY  APPLICATIONS. 

Judgment  upon  the  analytic  results  from  a 
given  sample  of  water  depends  upon  the  class  to 
which  it  belongs,  and  to  the  particular  influences 
to  which  it  has  been  subjected.  A  proportion  of 
total  solids  which  would  be  suspicious  in  a  rain  or 
river  water,  would  be  without  significance  in  that 
from  an  artesian  well.  On  the  other  hand,  a 
subsoil  water  of  unobjectionable  character  would 
contain  a  proportion  of  nitrates  which  would  be 
inadmissible  in  the  case  of  a  river  or  deep  water. 
Location  has  also  much  bearing  in  the  case ;  sub- 
soil waters  near  the  sea  will  be  found  to  contain, 
without  invoking  suspicion,  proportions  of  chlorin 
which  would  be  ample  to  condemn  the  same 
sample  if  derived  from  a  point  far  inland.  Hence 
the  importance  of  recording,  at  the  time  of  collec- 
tion, all  ascertainable  information  as  to  the  sur- 
roundings and  probable  source  of  the  water. 


SANITARY    APPLICATIONS.  II 7 

Analyses  of  surface  waters  have  no  value  unless 
supplemented  by  a  careful  survey  of  the  watershed 
to  determine  sources  of  pollution.  Such  survey 
will  often  discover  conditions  sufficient  to  con- 
demn the  supply,  even  though  the  analyses  may 
be  satisfactory.  Indeed,  it  may  be  taken  as  a 
fundamental  principle  that  surface  water  from 
even  a  sparsely  populated  district  will  be  unsafe 
for  use  unless  efficiently  filtered. 

Color,  Odor,  and  Taste. — Water  of  the  highest 
purity  will  be  clear,  colorless,  odorless,  and  nearly 
tasteless.  While  in  some  cases  a  decided  de- 
parture from  this  standard  may  give  rise  to  sus- 
picion, analytic  observations  are  necessary  to 
decide  the  point.  Water  highly  charged  with 
mineral  matters  will  possess  decided  taste,  vege- 
table matters  may  communicate  distinct  color; 
but,  on  the  other  hand,  it  may  be  highly  con- 
taminated with  dangerous  substances  and  give 
no  indications  to  the  senses.  Well-waters  oc- 
casionally become  offensive  in  odor,  from  pene- 
tration of  tree  roots.  The  odor  often  recalls  that 
of  hydrogen  sulfid.  Sulfids  are,  indeed,  often 
formed  in  such  cases  by  the  abstraction  of  oxygen 
from  sulfates  under  the  influence  of  microbes. 
Such  waters  are  often  used  without  apparent  in- 
jury, but  it  is  probable  that  if  direct  pollution 
occurs,  the  danger  would  be  enhanced  by  the 
presence  of  the  vegetable  matter. 


Il8       INTERPRETATION  OF  RESULTS. 

Surface  waters  collected  in  reservoirs  or  ponds 
often  become  very  offensive  from  the  growth  of 
algae,  but  apart  from  the  disgust  created  by  the 
water,  it  is  not  known  that  any  harmful  results 
occur  to  those  using  it. 

Turbidity  may  be  due  to  several  causes,  of 
different  degrees  of  danger,  but  is  always  objec- 
tionable. 

Total  Solids. — Excessive  proportions  of  mineral 
solids,  especially  of  marked  physiologic  action,  are 
known  to  render  water  non-potable,  but  no 
absolute  maximum  or  minimum  can  be  assigned 
as  the  limit  of  safety.  Distilled  water  and  waters 
very  highly  charged  with  mineral  matter  have 
been  used  for  long  periods  without  ill  effects. 
The  popular  notion  that  the  so-called  hard  waters 
conduce  to  the  formation  of  urinary  calculi  is  not 
borne  out  by  surgical  experience  or  statistical 
inquiry.  Many  urinary  calculi  are  composed  of 
uric  acid,  and  are  the  results  of  disorders  of  the 
general  nutritive  functions. 

Sanitary  authorities  have  fixed  an  arbitrary 
limit  of  total  solids  of  about  six  hundred  parts  per 
million,  but  many  artesian  waters  in  constant  use 
exceed  this. 

The  odor  produced  on  heating  the  water  residue 
is  often  of  much  use  in  detecting  contamination. 
Odors  similar  to  those  produced  by  heating  glue, 
hair,  rancid  fats,  urine,  or  other  animal  products. 


SANITARY    APPLICATIONS.  II9 

will  give  rise  to  grave  suspicion.  On  the  other 
hand,  a  more  favorable  judgment  may  be  given 
when  the  odor  recalls  those  given  off  in  the  heating 
of  non-nitrogenous  vegetable  materials,  such  as 
wood-fiber. 

Poisonous  Metals. — The  proportion  of  iron  in 
water  constantly  used  for  drinking  purposes  should 
not  much  exceed  three  parts  per  million.  Lead, 
copper,  arsenic,  and  zinc  must  be  considered 
dangerous  in  any  amount,  tho  it  appears  that 
zinc  and  copper,  being  least  cumulative,  are  rather 
less  objectionable  in  minute  amount  than  the 
others.  Concerning  the  limit  of  safety  with 
manganese  and  chromium  very  little  is  known, 
but  their  presence  in  appreciable  quantity  must 
be  looked  upon  with  suspicion. 

Chlorids  and  Phosphates. — Chlorids — principally 
sodium  chlorid — and  phosphates  are  abundantly 
distributed  in  rocks  and  soils,  and  find  their  way 
into  natural  waters;  but  while  the  former  are 
freely  soluble  and  remain  in  undiminished  amount 
under  all  conditions  to  which  the  water  is  sub- 
jected, all  but  small  amounts  of  the  latter  are 
either  precipitated  or  removed  by  the  action  of 
living  organisms.  Surface  and  subsoil  waters 
ordinarily  contain  but  a  few  parts  per  million. 
Both  chlorids  and  phosphates  being  constant  and 
characteristic  ingredients  of  animal  excretions, 
it  is  obvious  that  an  excess  of  them  in  natural 


120       INTERPRETATION  OF  RESULTS. 

waters,  unless  otherwise  accounted  for,  will 
suggest  direct  contamination.  Proximity  to  lo- 
calities in  which  sodium  chlorid  is  abundant,  such 
as  the  sea-  or  salt-deposits,  will  deprive  the  figure 
for  the  chlorin  of  diagnostic  value,  nor  can  any 
indication  of  sewage  or  other  dangerous  pollution 
be  inferred  from  high  proportion  of  chlorin  in 
deep  waters.  Further,  it  has  been  shown  that  the 
proportion  of  chlorin  in  uncontaminated  waters 
is  tolerably  constant,  while  in  water  subjected  to 
the  infiltration  of  sewage  the  chlorin  undergoes 
marked  variation  in  amount.  In  most  cases, 
therefore,  a  correct  judgment  can  only  be  attained 
by  comparison  with  the  average  character  of  the 
waters  of  the  same  type  in  the  district,  and  by 
examination  at  intervals  of  the  water  in  question. 

As  regards  phosphates,  Hehner,  who  has  pub- 
lished a  series  of  analyses,  states  that  the  presence 
of  more  than  0.6  part  per  million — calculated  as 
PO4 — should  be  regarded  with  suspicion.  On  the 
other  hand,  the  absence  of  phosphates  affords  no 
positive  proof  of  the  freedom  from  pollution. 
Woodman,  who  has  carefully  investigated  this 
question,  regards  Hehner 's  limit  as  too  strict.  He 
would  fix  I  part  per  million  as  the  minimum. 
He  regards  this  datum  as  valuable  in  judging  of 
the  sanitary  quality  of  the  sample. 

Nitrogen  from  Ammonium  Compounds. — Am- 
monium compounds  are  usually  the  results  of  the 


SANITARY   APPLICATIONS.  121 

putrefactive  fermentation  of  nitrogenous  organic 
matter;  they  may  also  be  the  product  of  the  re- 
duction of  nitrites  and  nitrates  in  presence  of 
excess  of  organic  matter.  In  either  case,  there- 
fore, they  suggest  contamination.  Deep  waters 
often  contain  an  excess  of  ammonium  compounds, 
derived,  in  large  part,  from  the  reduction  of 
nitrates.  Their  presence  here  is  hardly  ground 
for  adverse  judgment,  since  the  water,  even  tho 
originally  contaminated,  has  undergone  extensive 
filtration  and  oxidation,  its  organic  matter  con- 
verted into  bodies  presumably  harmless,  and 
microbes  have  perished.  Such  waters,  indeed, 
usually  show  only  traces  of  unchanged  organic 
matter. 

Rain  water  often  contains  large  proportions  of 
ammonium  compounds;  but  here,  also,  the  fact 
can  not  condemn  the  water,  since  it  does  not  in- 
dicate contamination  with  dangerous  organic 
matter. 

Nitrogen  by  Alkaline  Permanganate  (Nitrogen  of 
''Albuminoid  Ammonia"). — A  large  yield  of  am- 
monia by  boiling  with  alkaline  potassium  per- 
manganate will,  of  course,  point  to  an  excess  of 
nitrogenous  organic  matter.  The  inferences  to  be 
drawn  depend  upon  the  origin  and  condition  of 
the  organic  material.  If  animal,  the  water  may 
at  once  be  condemned  as  unsafe.  Waters  con- 
taining   excessive    amounts    even    of    vegetable 


122       INTERPRETATION  OF  RESULTS. 

matter  are  not  free  from  objection,  since  they  have 
frequently  caused  persistent  diarrhea.  If  the 
organic  matter,  whether  animal  or  vegetable,  is  in 
a  state  of  active  decomposition,  it  is  doubly 
objectionable. 

Smart  has  observed  that  water  containing 
fermenting  vegetable  matter  is  colored  yellow  by 
boiling  with  sodium  carbonate. 

Inferences  as  to  the  source  of  the  organic  matter 
can  usually  be  drawn  from  the  amount  of  chlorin 
and  nitrates  present.  If  the  chlorin  is  high, — 
i.  e.,  in  excess  of  the  average  of  the  district, — it 
may  be  inferred  that  the  material  is,  in  great  part, 
of  animal  origin.  In  this  case  the  nitrates  will 
either  be  high  or  entirely  absent,  according  as 
the  contaminating  matter  has  passed  through  soil 
or  enters  the  water  directly. 

A  large  amount  of  vegetable  matter  will,  as  a 
rule,  show  itself  by  color  imparted  to  the  water. 

Total  Nitrogen. — Drown  and  Martin's  results 
with  surface  waters  indicate  that  the  total  nitrogen 
obtained  by  their  process  is  about  twice  that  ob- 
tained by  alkaline  permanganate.  The  experi- 
ments made  by  Dr.  Beam  and  myself  accord  with 
this.  Further  observation  on  different  waters  • 
and  by  different  observers  will  be  required  to 
determine  the  value  to  be  assigned  to  the  figures 
obtained  by  this  method.  This  method  is  es- 
pecially suitable  for  studying  the  effects  of  filtra- 


SANITARY    APPLICATIONS.  I23 

tion,  storage,  etc.,  on  the  nitrogenous  organic 
matter  in  water. 

Nitrogen  as  Nitrites. — Nitrites  are  present  in 
water  as  the  result  either  of  incomplete  nitrifica- 
tion of  ammonium,  or  the  reduction  of  already- 
formed  nitrates,  under  the  influence  of  reducing 
agents  or  microbes.  Since  they  are  transition 
products,  their  presence  in  water  is  usually  evi- 
dence of  existing  fermentative  changes,  and, 
further,  may  be  taken  as  indicating  that  the  water 
is  unable  to  dispose  of  the  organic  contamination. 
When,  however,  the  conditions  are  such  that  oxi- 
dation can  not  take  place,  nitrites  may  persist  for 
a  long  time.  This  sometimes  occurs  in  deep 
waters  in  which  fermentative  changes  have  long 
since  ceased,  but  oxygen  is  not  available.  These 
contain  not  infrequently  small  amounts  of  nitrites, 
to  which  the  same  degree  of  suspicion  can  not  be 
attached.  When  nitrites  are  found  in  these 
waters,  the  possibility  of  their  introduction  from 
polluted  subsoil  water,  thru  defective  tubing, 
must  not  be  overlooked.  Rain  water,  also,  some- 
times contains  nitrites  derived  from  the  air,  and 
therefore  not  indicative  of  any  putrefactive 
change.  The  presence  of  measurable  quantities 
of  nitrites  in  river  or  subsoil  water  is  sufficient 
ground  for  condemnation. 

Nitrogen  as  Nitrates. — Nitrates  are  the  final 
point    in    the    oxidation    of   nitrogenous    organic 


124      INTERPRETATION  OF  RESULTS. 

matter,  especially  animal  matters.  Rain  water 
and  that  from  mountain  streams  and  deep  wells, 
except  from  cretaceous  strata,  generally  contain 
only  traces,  but  river  and  subsoil  waters  will 
always  contain  appreciable  amounts,  unless  some 
reducing  action,  such  as  recent  sewage -pollution, 
is  at  work.  When,  therefore,  a  water  contains 
enough  mineral  matter  to  demonstrate  its  perco- 
lation thru  soil,  and  at  the  same  time  is  free  from 
nitrates  or  contains  only  traces,  the  occurrence 
of  a  destructive  fermentation  may  be  inferred. 
These  cases  are  not  uncommon  among  well-waters, 
and  the  samples  are  generally  turbid  from  sus- 
pended organic  matter.  Decided  departure, 
either  by  increase  or  decrease,  from  the  proportion 
of  nitrates  usual  in  the  same  class  of  water  in  any 
district  may  be  taken  as  evidence  of  contamination. 
Oxygen-consuming  Power. — Sanitary  authori- 
ties differ  very  much  as  to  the  significance  of  this 
datum.  Attempts  have  been  made  to  fix  maxi- 
mum limits  for  the  various  types  of  water,  and 
also  to  gage  the  character  and  condition  of  the 
organic  matter  by  observing  the  rate  at  which  the 
oxidation  takes  place,  but  no  positive  conclusions 
can  be  given.  In  general,  it  may  be  said  that  a 
sample  which  has  high  oxygen-consuming  power 
will  be  more  likely  to  be  unwholesome  than  one 
which  is  low  in  this  respect ;  but  the  interferences 
are  so  numerous,  and  the  susceptibility  to  oxida- 


SANITARY    APPLICATIONS.  12  5 

tion  of  different  organic  matters,  of  even  the  same 
type,  is  so  different,  that  the  method  is  at  best 
only  of  accessory  value.  It  is  especially  suitable 
for  consecutive  determinations  on  the  same  supply. 
The  following  proportions  are  given  by  Frank- 
land  and  Tidy  as  the  basis  of  interpreting  the 
results  of  this  method : 

Oxygen  Absorbed  in  Three 
Hours. 

High  organic  purity,     .0.05  part  per  million. 

Medium  purity, 0.5    to  1.5  parts  '* 

Doubtful, 1. 5    to  2.1     "       " 

Impure, over  2.1  ''       ''         ** 

For  the  method  with  acidified  permanganate  at 
the  boiling  heat,  the  German  chemists,  who 
employ  it  largely,  regard  an  absorption  of  2.5  parts 
of  oxygen  per  million  as  suspicious,  and  some 
sanitary  authorities  have  fixed  3.8  parts  of  oxygen 
per  million  as  the  highest  permissible  limit. 

Dissolved  Oxygen. — Full  aeration  of  water  is 
favorable  to  the  destruction  of  organic  matter; 
a  decided  diminution  in  the  quantity  of  dissolved 
oxygen  may  show  excess  of  such  matter  and  >  of 
microbic  life.  These  changes  are  more  likely  to 
take  place  in  still  waters,  and  are  frequently  ac- 
companied by  disagreeable  odor  and  taste.  In 
cases  in  which  stored  waters  become  unpalatable, 
these  facts  should  be  borne  in  mind. 


126      INTERPRETATION  OF  RESULTS. 

Hardness. — The  degree  of  hardness,  unless  very 
high,  has  but  httle  bearing  on  the  sanitary  value 
of  water,  but  is  important  in  reference  to  its 
use  for  general  household  purposes,  in  view  of  the 
soap-destroying  power  which  hard  waters  possess. 


USUAL    ANALYTIC    RESULTS    FROM    UNCONTAMI- 
NATED  WATERS. 

Milligrams  per  Liter. 

Rain.  Surface.          Subsoil.               Deep. 

Total  solids, 5  to  20  15  upward      30  upward         45  upward 

Chlorin, Traces  to  i  i  to  10            2  to  12        Traces  to  large 

quantity 
Nitrogen     by    per- 
manganate, ....     0.08  to  0.20  o.os  to  0.15    0.05  to  o.io       0.03  to  o.io 
Nitrogen     as     am- 
monium,       0.20  to  0.50  0.00  to  0.03    0.00  to  0.03    Generally  high 

Nitrogen  as  nitrites,       None  or  None               None          None  or  traces 

traces 
Nitrogen      as      ni- 
trates,           Traces  0.75  to  1.25        1.5  to  5             0.00  to  3 


Inferences  from  Culture  Methods. — No  absolute 
limit  as  to  the  number  of  ordinary  microbes  can 
be  fixed.  Some  bacteriologists  have  fixed  the 
maximum  of  loo  per  cubic  centimeter,  but  this  is 
arbitrary.  An  appreciable  number  of  microbes 
of  the  colon  class  will  be  a  basis  for  condemnation 
of  the  water. 

There  is,  however,  one  field  of  inquiry  in  which 
even  mere  microbe-counting  has  value ;  that  is,  in 
comparing  samples  of  the  same  water  before  and 
after  some  treatment  for  purification  or  in  some 
other  incident.  In  these  studies  the  method .  is 
sufficiently  free  from  fallacy  to  make  the  results 
trustworthy  when  they  are  conducted  in  a  strictly 


ACTION    OF    WATER    ON    LEAD.  1 27 

uniform  manner ;  thus,  if  a  river  water  supplied  to 
a  filter  is  studied  daily  by  repeated  examination  of 
samples  before  and  after  filtration,  inoculating 
separate  portions  of  the  same  culture -medium, 
and  multiplying  the  results  to  such  an  extent  as 
to  eliminate  accidental  differences,  a  comparison 
between  the  water  before  and  after  filtration  may 
be  safely  made  as  to  the  proportion  of  microbes 
removed.  Moreover,  special  microbes  of  highly 
characteristic  properties  may  be  introduced  in 
large  quantities  into  the  water,  and  by  subsequent 
culture  the  extent  to  which  these  are  removed  may 
be  satisfactorily  recognized. 

ACTION  OF  WATER  ON  LEAD. 
The  almost  universal  use  of  lead  pipes  for  con- 
veying water,  and  the  facility  with  which  some 
waters  corrode  and  dissolve  the  metal,  make  it  a 
question  of  moment  to  determine  the  cause  of  this 
action  and  to  devise  means  for  its  prevention. 
As  a  rule,  it  is  found  that  waters  free  from  mineral 
matter  dissolve  lead  with  facility,  especially  in  the 
presence  of  oxygen.  Some  very  soft  waters  are 
entirely  without  action.  Messrs.  Crookes,  Odling, 
and  Tidy  found  that  the  action  was  controlled  by 
the  amount  of  siHca  contained  in  the  water. 
They  found  that  those  soft  waters  which,  when 
taken  from  the  service  pipes,  contained  a  notable 
quantity  of  lead,  gave,  on  the  average,  three  parts 


128  INTERPRETATION    OF    RESULTS. 

of  silica  per  million ;  in  those  in  which  there  was  no 
lead,  the  silica  present  amounted  to  7.5  per  million, 
and  in  those  in  which  the  action  was  intermediate, 
5.5.  parts  per  million.  That  it  was  really  the 
silica  that  conditioned  the  corrosion  was  con- 
firmed by  laboratory  experiments.  They  also 
found  that  the  most  effective  way  of  silicating  a 
water  is  by  passing  it  over  a  mixture  of  fiint  and 
limestone.  The  reason  for  this  was  pointed  out 
later  by  Messrs.  Camelly  and  Frew,  who  showed 
that  while  calcium  carbonate  and  silica  both  exert 
a  protective  influence,  calcium  silicate  is  more 
effective  than  either;  and,  further,  that  in  almost 
all  cases  in  which  corrosion  took  place,  it  was 
greater  in  the  presence  of  oxygen.  This  is  partic- 
ularly the  case  with  potassium  and  ammonium 
nitrates  and  with  calcium  hydroxid.  The  reverse 
is  true  of  calcium  sulfate,  which  is  more  corrosive 
when  air  is  excluded.  Their  experiments  also 
show  that  the  presence  of  calcium  carbonate  or 
calcium  silicate,  altogether  prevents  corrosion  by 
potassium  and  ammonium  nitrates. 

As  the  result  of  an  elaborate  series  of  experi- 
ments Miiller  concludes  that,  while  chlorids, 
nitrates,  and  sulfates  all  act  upon  lead  pipes,  no 
corrosion  takes  place  in  the  presence  of  sodium 
acid  carbonate,  and  that  calcium  carbonate,  by 
taking  up  carbonic  acid,  acts  in  the  same  way. 
This  latter  conclusion   is   at  variance   with   the 


TECHNIC    APPLICATIONS. 


129 


observations  of  Carnelly  and  Frew,  who  found 
that  calcium  carbonate  is  equally  effective  when 
carbonic  acid  is  excluded.  MuUer  also  states  that 
surface  waters,  contaminated  by  sewage  and 
containing  large  amounts  of  ammoniacal  com- 
pounds, will  dissolve  lead  under  all  circumstances. 

Allen  has  shown  that  water  containing  free  acid, 
including  sulfuric  acid,  acts  energetically  upon 
lead.  This  is  not  surprising  in  view  of  the  later 
experiments,  which  prove  that  even  calcium 
sulfate  is  corrosive.  Later,  W.  Carleton- Williams 
found  that  even  in  the  presence  of  free  acid,  cor- 
rosion may  be  prevented  by  the  addition  of  suffi- 
cient silica.  His  experiments  also  confirm  the 
view  generally  held,  that  soluble  phosphates  pro- 
tect lead  to  a  marked  degree. 

The  following  is  a  summary  of  the  more  im- 
portant observations  on  this  subject : 

Corrosive :  Free  acid  or  alkalis,  oxygen,  nitrates, 
particularly  potassium  and  ammonium  nitrates, 
chlorids,  and  sulfates. 

Non-corrosive  and  preventing  corrgsion  by  the 
above:  Calcium  carbonate,  sodium  acid  carbon- 
ate, ammonium  carbonate,  calcium  silicate,  silica, 
and  soluble  phosphates. 

TECHNIC  APPLICATIONS. 
Boiler  Waters. — The  main  conditions  affecting 
the  value  of  a  water  for  steam-making  purposes 


130  INTERPRETATION    OF    RESULTS. 

are  its  tendency  to  cause  corrosion  and  the  forma- 
tion of  scale.  Corrosion  may  be  due  to  the  water 
itself,  to  the  presence  of  free  acids,  or  to  sub- 
stances which  form  acids  under  the  influence  of 
the  heat  to  which  the  water  is  subjected.  Pure 
water — e.  g.,  distilled  water — exhibits  a  power- 
fully corrosive  action  upon  iron.  The  dissolved 
oxygen  which  all  waters  contain  also  aids  in  the 
corrosion,  and  especially  when  accompanied,  as  is 
usually  the  case,  by  carbonic  acid.  There  is 
always  greater  rusting  at  the  point  at  which  the 
water  enters  the  boiler,  since  there  the  gases  are 
driven  out  of  solution  and  immediately  attack  the 
metal.  This  is  an  evil  that  obtains  with  all 
waters,  and  it  is  not  customary,  in  making  ex- 
amination for  technic  purposes,  to  determine  the 
amount  of  these  bodies.  In  water  that  has  had 
free  access  to  air,  the  oxygen  in  solution  is  a 
tolerably  constant  quantity,  and  it  is  sufficient 
to  note  the  temperature  and  refer  to  the  table  of 
amounts  of  oxygen  dissolved  in  water.  The 
corrosive  action  of  oxygen  and  carbonic  acid  is 
especially  noticeable  in  waters  that  are  com- 
paratively pure,  such  as  those  derived  from  moun- 
tain springs.  This  was  repeatedly  observed  by 
Dr.  William  Beam,  in  the  examination  of  the 
waters  used  for  the  locomotives  of  the  Baltimore 
and  Ohio  Railroad.  The  waters  which  caused 
the  most  corrosion  were  mainly  those  containing 


TECHNIC    APPLICATIONS.  I31 

small  quantities  of  solid  matter,  the  full  amount 
of  oxygen,  and  considerable  carbonic  acid,  but  no 
other  acid  or  acid-forming  body.  Waters  of  this 
type  are  often  materially  improved  by  adding  a 
small  amount  of  slaked  lime. 

Free  acid,  other  than  carbonic  acid,  is  not  often 
found  in  water,  and  if,  present,  renders  the  water 
unfit  for  use,  unless  it  be  neutralized.  Mine 
waters  are  the  most  likely  to  contain  free  acid, 
sulfuric  acid  being  generally  present.  Sometimes 
the  acidity  is  due  to  organic  acids.  These  act 
very  injuriously  on  iron. 

Magnesium  chlorid  is  frequently  present  in 
waters,  and  if  in  considerable  quantity,  may  be 
very  harmful.  At  a  temperature  of  310°  F., 
corresponding  to  an  effective  pressure  of  four  at- 
mospheres, magnesium  chlorid  reacts  with  water 
to  form  magnesium  oxid  and  hydrochloric  acid, 
the  latter  attacking  the  boiler,  especially  at  the 
water-line.  If  considerable  calcium  carbonate  is 
present,  the  evil  may  be  somewhat  lessened,  but, 
as  Allen  has  pointed  out,  and  as  we  also  have 
noticed,  there  may  still  be  corrosion,  so  that  the 
presence  of  more  than  a  small  quantity  of  the  salt, 
say  a  grain  or  two  to  the  gallon,  may  be  considered 
objectionable.  Allen  remarks  that  the  presence 
of  a  certain  amount  of  sodium  chlorid  may  pre- 
vent this  decomposition,  the  two  chlorids  com- 
bining to  form  a  stable  double  salt.     The  addition, 


132      INTERPRETATION  OF  RESULTS. 

therefore,  of  common  salt  to  a  water  containing 
magnesium  chlorid  may  act  to  diminish  corrosion, 
a  point  which  will  bear  further  investigation. 

It  has  not  been  determined  how  far  the  presence 
of  nitrites,  nitrates,  and  ammonium  compounds 
affects  the  quality  of  water  for  steam-making 
purposes ;  but  it  is  more  than  probable  that  they 
act  harmfully,  especially  the  nitrates,  which  are 
frequently  present  in  large  amount. 

Scale  is  composed  of  matters  deposited  from  the 
water  either  by  the  decompositions  induced  by  the 
heat  or  by  concentration.  When  the  deposit  is 
loose,  it  is  termed  sludge  or  mud,  and  usually  con- 
sists of  calcium  carbonate,  magnesium  oxid,  and 
a  small  amount  of  magnesium  carbonate.  The 
magnesium  oxid  is  formed  by  the  decomposition 
of  the  magnesium  carbonate  and  chlorid. 

The  formation  of  sludge  is  the  least  objec- 
tionable effect,  since  it  may  readily  be  removed 
by  ''blowing  off,''  provided  that  care  is  previously 
taken  to  allow  the  flues  to  cool  down  so  that  when 
the  water  is  removed  the  heat  of  the  flues  may  not 
bake  the  deposit  to  a  hard  mass.  Waters  con- 
taining calcium  sulfate  form  hard  incrustations 
difficult  to  remove  and  causing  great  loss  of  fuel 
by  interfering  with  the  transmission  of  the  heat  to 
the  water.  It  not  only  forms  a  hard  incrustation 
in  itself,  but  becomes  incorporated  with  the  mud, 
and  renders  it  also  hard.     The  hard  scale  will  also 


TECHNIC    APPLICATIONS.  I33 

contain  practically  all  the  silica  and  the  iron  and 
aluminum  present  in  the  water,  besides  any 
matters  originally  held  in  suspension. 

It  follows  from  the  above  that  a  water  only 
temporarily  hard  will,  if  care  is  taken  in  the 
management  of  the  boiler,  cause  the  formation 
merely  of  a  loose  deposit  of  sludge — temporary 
hardness  being  due  in  the  main  to  calcium  and 
magnesium  carbonates.  A  water  permanently 
hard  will  probably  form  a  hard  scale,  since  such 
hardness  is  usually  due  to  calcium  sulfate. 

In  accordance  with  these  principles,  the  analysis 
of  a  water  for  steam-making  purposes  may  include 
the  determinations  of  free  acid,  total  solid  residue, 
sulfates,  chlorin,  calcium,  magnesium,  temporary 
and  permanent  hardness.  In  cases  in  which 
the  qualitative  tests  show  but  small  amounts  of 
sulfates  and  chlorin,  the  analysis  may  be  limited 
to  the  determinations  of  the  temporary  and  per-  ■ 
manent  hardness. 

In  the  laboratory  of  the  Pennsylvania  Railroad 
an  approximate  determination  of  scale-forming  in- 
gredients has  been  made  in  the  following  manner : 
The  total  solids  obtained  by  evaporation  are 
treated  with  diluted  alcohol  (fifty  per  cent.), 
and  the  undissolved  residue  is  denominated 
' '  scale-forming  material. ' ' 

It  has  been  pointed  out  in  an  earlier  chapter 
that  it  is  not  possible  to  deduce  from  the  analytic 


134  INTERPRETATION    OF    RESULTS. 

result  the  exact  forms  in  which  the  various  ele- 
ments are  combined,  but  since  it  is  known  that  at 
the  high  temperature  ordinarily  reached  in  boilers 
definite  chemical  changes  occur,  it  is  safest  to 
exhibit  the  maximum  amount  of  corrosive  and 
scale -forming  ingredients  which  the  water  under 
these  circumstances  could  develop.  Thus,  since 
calcium  sulfate  is  practically  insoluble  in  water 
above  212^  F.,  the  proportion  of  calcium  sulfate 
may  be  regarded  as  such  as  would  be  formed  by 
the  total  quantity  of  calcium  or  the  total  quantity 
of  SO  4,  according  to  which  is  present  in  the  larger 
amount.  Similarly,  as  the  decomposition  of  mag- 
nesium chlorid  is  induced  by  the  high  temperature 
of  the  boiler,  the  analytic  statement  should  in- 
dicate the  maximum  proportion  of  this  compound 
obtainable  from  the  magnesium  and  chlorin  pres- 
ent. These  rules  can  not  apply  absolutely  to 
waters  rich  in  alkali  carbonates,  since  these  would 
neutralize  any  acid  formed  from  the  magnesium 
chlorid,  or  even  prevent  its  formation,  and  would 
prevent,  to  a  large  extent,  the  formation  of  calcium 
sulfate.  Much  remains  to  be  determined  con- 
cerning the  effects  of  the  high  temperature  and 
concentration  to  which  boiler  waters  are  subjected. 
General  Technic  Uses. — In  regard  to  the  quality 
of  water  for  technic  other  than  steam-making 
purposes,  such  as  brewing,  dyeing,  tanning,  etc., 
no   detailed  methods   or  standards   can  be   laid 


TECHNIC    APPLICATIONS.  I35 

down.  The  nearest  approach  to  purity  that  can 
be  secured  in  the  supply  will  be  of  the  greatest 
advantage.  The  more  objectionable  qualities 
will  be  large  proportion  of  organic  matter,  es- 
pecially if  it  distinctly  colors  the  water,  excessive 
hardness,  and  notable  amounts  of  iron  or  free 
mineral  acid.  It  is  said  that  one  part  of  iron  per 
million  will  render  water  unsuitable  for  bleaching 
establishments.  It  has  been  noted  that  a  large 
proportion  of  active  microbes  is  injurious  in  the 
manufacture  of  indigo.  In  artificial  ice  making, 
a  very  pure  water  must  be  used  if  a  clear  and 
colorless  product  be  desired.  Any  suspended  or 
dissolved  coloring-matter  will  be  concentrated  by 
the  freezing  and  appear  in  the  bottom  or  center  of 
the  mass. 

The  examination  of  sewage-effluents  and  waste 
waters  from  manufacturing  establishments  is  to 
be  conducted  upon  the  same  principles  as  for 
ordinary  supplies,  but  especial  attention  must  be 
given  to  the  presence  of  poisonous  metals  and  free 
mineral  acids.  The  latter  interfere  with  the  nor- 
mal self -purification  of  the  water.  For  the  nitro- 
gen determination,  the  Kjeldahl  process  will  be 
found  more  satisfactory  than  that  by  alkaline 
permanganate. 


136      INTERPRETATION  OF  RESULTS. 

PURIFICATION  OF  WATER. 

The  purification  of  drinking  water  is  a  question 
of  sanitary  engineering  that  is  outside  the  scope  of 
this  work. 

Purification  of  Boiler  Waters. — The  problems 
present  in  the  treatment  of  boiler  waters  are 
usually  the  removal  of  the  calcium  carbonate  and 
sulfate,  and  magnesium  carbonate  and  chlorid. 
Both  carbonates  are  appreciably  soluble  in  pure 
water.  About  1 5  parts  of  calcium  carbonate  per 
million  is  usually  stated  to  be  the  proportion  dis- 
solved, but  it  has  been  pointed  out  by  Allen  that 
solutions  can  be  obtained  containing  twice  this 
amount.  If  the  water  contains  carbonic  acid,  it 
will  take  up  a  much  greater  proportion  of  the  car- 
bonates, but  in  this  case  they  will  be  deposited 
from  the  solution  by  boiling.  This  has  been  ac- 
counted for  by  supposing  the  existence  of  soluble 
bicarbonates,  which  are  decomposed  by  the 
boiling.  Nearly  all  of  these  carbonates  can  be 
thrown  out  of  solution  by  any  means  that  will 
deprive  the  water  of  the  carbonic  acid.  ^Sodium 
hydroxid  is  often  employed  for  the  purpose,  and 
should  be  added  in  quantity  just  sufficient  to  form 
normal  sodium  carbonate.  If  there  are  present 
in  the  water  calcium  and  magnesium  chlorids  and 
sulfates,  these  also  will  be  decomposed  and  precipi- 
tated by  the  sodium  carbonate  so  formed.     If  the 


PURIFICATION    OF    WATER.  I37 

amount  of  sodium  carbonate  formed  is  not  suffi- 
cient to  decompose  all  of  these  bodies,  a  sufficient 
quantity  should  be  added  with  the  sodium  hy- 
droxid  to  effect  the  complete  decomposition. 
The  precipitate  is  allowed  to  settle  or  filtered  off. 

In  cases  in  which  the  feed-water  is  heated  be- 
fore it  enters  the  boiler,  it  may  only  be  necessary 
to  add  to  the  water  sodium  carbonate  in  quantity 
sufficient  to  decompose  the  calcium  and  mag- 
nesium chlorids  and  sulfates,  since  the  heat  alone 
will  suffice  to  throw  down  the  carbonates. 

Care  should  be  taken  in  these  precipitations 
that  no  more  sodium  hydroxid  is  added  than  is 
required  for  the  precipitation,  since  any  excess 
would  tend  to  corrode  the  boiler. 

Clark's  process  consists  in  treating  the  water 
with  calcium  hydroxid  (lime-water).  This  pre- 
cipitates the  calcium  and  magnesium  carbonates 
by  depriving  the  water  of  its  free  carbonic  acid. 
It  has,  of  course,  no  effect  upon  the  calcium  sulfate. 
It  is  to  be  noted  that  the  proportion  of  calcium 
hydroxid  which  is  to  be  added  must  be  calculated 
from  the  amount  of  free  carbonic  acid  existing  in 
the  water,  and  not  from  the  amount  of  carbonates 
to  be  removed.  The  precipitate  will  usually  re- 
quire at  least  twelve  hours  for  complete  subsidence, 
but  after  three  or  four  hours  the  water  will  be 
sufficiently  clear  for  some  purposes.  If  a  filter 
press  is  used,  as  in  Porter's  process,  the  time  re- 


138  INTERPRETATION    OF    RESULTS. 

quired  for  clarification  is  very  much  shortened. 
Another  advantage  of  this  process  is  the  use  of  a  so- 
lution of  silver  nitrate,  in  order  to  determine  more 
conveniently  the  proportion  of  calcium  hydroxid 
which  is  to  be  employed.  The  lime  is  first  slaked 
and  dissolved  in  water,  and  the  water  to  be  soft- 
ened run  in  and  well  mixed  with  it.  From  time  to 
time  small  portions  are  taken  out  and  a  few  drops 
of  a  solution  of  silver  nitrate  added.  As  long  as 
the  lime  is  in  excess,  a  brownish  coloration  is  pro- 
duced. When  this  has  become  quite  faint,  and 
just  about  to  disappear,  the  addition  of  the  water 
is  discontinued,  and,  after  a  short  time,  the  water 
is  filtered  by  means  of  the  press. 

Soluble  phosphates  added  to  a  water  precipitate 
completely  in  a  flocculent  condition  any  calcium, 
magnesium,  iron,  or  aluminum.  This  reaction 
can  be  best  applied  by  using  the  trisodium  phos- 
phate, which  is  now  a  commercial  article.  By 
reason  of  the  facility  with  which  this  substance 
loses  a  portion  of  its  sodium  to  acids,  it  acts  not 
only  as  a  precipitant  to  the  above  materials,  but 
will  neutralize  any  free  mineral  acid  present  in  the 
water.  From  evidence  submitted  by  those  who 
have  used  the  process  on  the  large  scale,  it  ap- 
pears that  not  only  is  no  hard  scale  formed,  but 
that  scale  already  existing  prior  to  its  use  is 
gradually   disintegrated   and   removed   with   the 


IDENTIFICATION  OF  THE  SOURCE  OF  WATER.    139 

sludge.  Experiments  indicate  that  no  injury 
results  from  an  excess  of  the  material;  but  the 
economical  employment  of  the  method,  especially 
with  very  hard  waters,  can  only  be  based  upon  a 
correct  analysis,  and  an  estimation  of  the  phos- 
phate required  for  the  precipitation.  In  many 
cases  the  composition  of  the  water  will  be  such  that 
a  partial  precipitation  will  be  sufficient. 

Considerable  success  has  been  obtained  by  the 
use  of  fluorids  as  precipitants  of  scale-forming 
elements.  Sodium  aluminate  has  also  been  re- 
commended. 

Waters  rich  in  ferrous  compounds  may  be 
purified  by  aeration  and  filtration,  the  iron  being 
separated  as  ferric  hydroxid. 

The  corrosive  action  of  very  pure  waters  is 
partially  abated  by  filtration  thru  bone  charcoal 
or  by  addition  of  small  amounts  of  lime. 


IDENTIFICATION  OF  THE  SOURCE  OF 
WATER. 
The  determination  of  the  course  of  underground 
streams,  and  of  communications  between  collec- 
tions of  water,  is  often  an  important  practical 
problem.  In  geologic  and  sanitary  surveys,  val- 
uable information  may  occasionally  be  gained. 
The  method  generally  pursued  when  connection 
between  water  at  accessible  points  is  to  be  de- 


I40      INTERPRETATION  OF  RESULTS. 

tected,  is  to  introduce  at  one  point  some  substance 
not  naturally  existing  in  the  water,  and  capable 
of  recognition  in  small  amount.  Lithium  com- 
pounds are  among  the  best  for  this  purpose. 
They  are  not  frequent  ingredients  of  natural 
waters,  and  are  easily  recognized  by  the  spec- 
troscope. Lithium  chlorid  is  the  most  suitable. 
The  quantity  to  be  employed  will  vary  with  cir- 
cumstances. It  scarcely  needs  to  be  stated  that 
the  waters  under  examination  should  be  carefully 
tested  for  lithium  before  using  the  method. 

When  the  lithium  method  is  inadmissible,  re- 
course must  be  had  to  other  substances  of  distinct 
character,  such  as  strontium  chlorid,  but  this 
possesses  the  disadvantage  that  a  considerable 
amount  may  be  rendered  insoluble,  and  thus  lost 
in  the  ordinary  transit  through  soil.  Use  has 
been  made  of  organic  coloring  matters  of  high 
tinctorial  power,  one  of  the  most  suitable  of  which 
is  fluorescein.  This  will  communicate  a  charac- 
teristic and  intense  fluorescence  to  many  thousand 
times  its  weight  of  water.  The  coloration  is 
distinct  only  in  alkaline  liquids.  Other  colors, 
such  as  anilin-red,  may  be  employed. 

A  more  important  feature  of  the  problem  from 
a  sanitary  point  of  view  is  the  determination  of 
the  source  of  a  given  current  or  collection  of  water, 
when  such  source  is  inaccessible.  Problems  of 
this  character  are  not  infrequent  in  large  cities  in 
which  the  systems  of  water-supply  and  drainage 


IDENTIFICATION  OF  THE  SOURCE  OF  WATER.    I4I 

are  defective,  thus  giving  occasion  to  accumu- 
lations of  water  in  cellars  and  similar  places. 
Often,  in  these  cases,  no  extended  explorations 
can  be  made,  by  reason  of  the  adjacent  buildings 
and  conflicting  property  interests,  and  the  ques- 
tion raay  arise  whether  the  water  proceeds  from 
a  leaky  hydrant,  drain,  sewer,  or  subsoil  current. 
It  is  obvious  that  in  the  case  of  the  collection  of 
water  in  a  cellar  from  causes  other  than  surface 
washings  or  entrance  of  rain,  it  must  have  passed 
thru  some  distance  of  soil,  and  in  built-up  dis- 
tricts will  almost  certainly  be  charged  with  or- 
ganic refuse.  To  correctly  interpret  the  results, 
it  will  be  necessary  to  know  the  general  character 
of  the  subsoil  water  of  the  district  and  the  com- 
position of  the  public  supply.  As  a  rule,  the 
transmission  of  water  thru  raoderate  distances 
of  soil  will  not  raaterially  increase  the  mineral 
constituents.  Hence,  if  the  sample  contains  an 
excess  of  dissolved  matters  as  compared  with  the 
water-supply  of  the  district,  it  may  reasonably  be 
inferred  that  it  is  derived  from  a  drain,  sewer,  or 
subsoil  current.  In  these  investigations  it  will 
generally  be  sufficient  to  determine  the  total  solids, 
odor  on  heating,  chlorin,  nitrates,  and  nitrites. 

Occasionally,  the  analytic  results  will  be  am- 
biguous, and  it  is  advisable  to  make  examinations 
of  more  than  one  sample,  since  accidental  cir- 
cumstances, rain-fall,  etc.,  may  affect  the  com- 
position of  the*  water. 


142 


INTERPRETATION    OF    RESULTS. 


DATA  FOR  CALCULATION 


Parts  per     100,000 

X     0.7 

=  grains  per 

Imperial 

a      u     1,000,000 

X     0.07 

n          a 

(( 

Loo^fOoa 

X    •0.583 

u         u           100,000 

X     0.583 

U.S. 

,,          ,,       1,000,000 

X     0.0^83 

a          n 

(( 

Grains  per  Imp.  gal 

.  X     1.429 

=  parts  per 

100,000 

"        "    ^," «    " 

X  14.29 

^^         ((            n 

1,000,000 

«      ..  u-  s.  .. 

X     1.724 

^^       u         u 

100,000 

it           n        n        ^^ 

X  17.24 

It         (( 

1,000,000 

Al,03 

X    0.53 

=  Al 

Agcl 

X     0.247 

=  C1 

BaSO^ 

X     0.42 

=  804 

BaSO^ 

X     0.343 

=  S03 

B2O3 

X     0.314 

=  B 

CaO 

X    0.7147 

=  Ca 

CaO 

X    1.785 

=  CaC03 

CaCOa 

X     0.4 

=  Ca 

CI 

X    1.65 

=  NaCl 

Fe^Os 

X     0.7 

=  Fe 

KCl 

X     0.525 

=  K 

K^PtCle 

X     0.161 

=  K 

K^PtCl^ 

X     0.307 

=  KC1 

Mg,PA 

X     0.2187 

=  Mg 

Mg^PA 

X     0.853 

=  P0, 

Mg^PA 

X    0.757 

=  MgCOs 

♦        Mg^PA 

X   0.6375 

=  P205 

MnS 

X     0.631 

=  Mn 

NaCl 

X     0.394 

=  Na 

N 

X   4.425 

=  N03 

N 

X     3.284 

=  N02 

N 

X   5.857 

=  Ca(N03)2 

N 

X     1.215 

=  NH3 

NH3 

X     0.822 

=  N 

ATOMIC   WEIGHTS. 


143 


ATOMIC  WEIGHTS 

(Report  International  Committee,  Jour.  Amer.  Chem.   Soc, 
Jan^ry,  1908.) 


Aluminum 27.1 

Barium I37'4 

Calcium 40.1 

Carbon 12.0 

Chlorin 35-45 

Chromium 52.1 

Copper 63.6 

Hydrogen 1.008 

lodin 126.97 

Iron 55.9 

Lead 206.9 

Lithium 7.03 


Magnesium 24.36 

Manganese 55.0 

Nitrogen 14.01 

Oxygen 16.0 

Phosphorus 31.0 

Platinum 194.8 

Potassium 39.15 

Silver 107.93 

Sodium 23.05 

Sulfur 32.06 

Zinc 65.4 


INDEX 


Agar,  73. 

media,  76. 

,  Hesse's,  88. 

Albuminoid  ammonia,  23,  32,121. 
Alizarin  indicator,  15. 
Alkaline  permanganate,  31. 
Alum,  detection,  60. 
Aluminum,  detection,  59. 

,  determination,  91. 

Aluminum  sulfate,  detection,  60. 
Ammonia,  albuminoid,  23,  32,  121. 

,  free,  23,  31,  120. 

method,  23. 

Ammonium  molybdate,  50. 
Analysis,  statement  of,  114. 
Arsenic,  detection,  56. 
Artesian  water,  i,  5. 
Atomic  weights,  143. 

Bacillus  colt  communis,  84. 

•  typhosus,  87. 

Bacteriologic  examinations,  70,  126. 
Barium,  55. 

Bile-lactose  medium,  86. 
Biologic  examinations,  63. 
Boiler  scale,  no,  132. 
Boiler  waters,  109,  129. 
Boric  acid,  109. 
Bouillon,  71. 
,  dextrose,  75. 

CALcroM,  determination,  92. 
Calculation  table,  142. 
Carbonic  acid,  determination,  107. 
Chlorin,  determination,  21. 

,  significance,  119, 

Chromium,  55. 
Clark's  process,  137. 
Classification  of  waters,  i. 
Colon  bacillus,  84-9. 
Color,  determination,  11. 

,  significance,  117. 

Condensers,  23. 
Copper,  detection,  62. 
,  determination,  63. 

Deep  water,  i,  5,  126. 
Denitrification,  5. 
Dextrose  bouillon,  75. 
Dissolved  oxygen,  52. 
Distilling  apparatus,  23. 

Free  ammonia,  23,  32,  37,  121. 

Ground  water,  1,  3. 
Gelatin,  73. 
medium,  76. 

Hardness,  ioi. 
Hesse's  agar,  88. 


Hydrogen  sulfid,  99. 

Indol  reaction,  83. 
Iron,  detection,  57. 
-Ih^ — ,  determination,  58,  91. 

Lactose-bile  medium,  86. 

litmus  medium,  80. 

Lead,  action  of  water  on,  127. 

,  detection,  61. 

,  determination,  62. 

Lithium,  determination,  98. 
Litmus-lactose  media,  80. 

Manganese  detection,  59. 

,  determination,  92,  94. 

Milk  medium,  79. 

Nessler  glasses,  29. 

— ; reagent,  30. 

Nitrates  39,  123. 

Nitrification,  4. 

Nitrites,  42,  123. 

Nitrogen  as  ammonium,  23,  32,  37  121. 

total  organic,  36,  122. 

Nitron  method,  41. 

Odor,  13,  117. 

Organic  and  volatile  matter,  19. 
Oxygen-consuming  power,  42,  124. 
,  dissolved,  52,  125. 

Permanganate,  alkaline,  31. 
Phenoldisulfonic  acid,  39. 
Phosphates,  50,  119. 
Poisonous  metals,  55,  119. 
Potassium,  determination,  95. 

Rain  water,  i,  2,  126. 
Reaction,  15. 

Samples,  collection,  8,  11. 

Scale,  no,  132. 

Silica,  91. 

Sludge,  132. 

Specific  gravity,  112. 

Spectroscopy,  in. 

Soap  test,  104. 

Subsoil  water,  i,  3   126. 

Sulfates,  94. 

Surface  water,  i,  2,  126. 

Taste,  117. 
Total  soUck,  16,  118. 
Turbidity,  14. 
Typhoid  bacillus,  87. 

Water,  classes  of,  i. 

Zmc,  detection,  56. 


144 


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Leffmann,   H.  Lk 

Examination  of  water   1?09 
for  sanitary  &  technic 
purposes • 


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